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2023-10-11binfmt_misc: enable sandboxed mountsChristian Brauner1-0/+10
Enable unprivileged sandboxes to create their own binfmt_misc mounts. This is based on Laurent's work in [1] but has been significantly reworked to fix various issues we identified in earlier versions. While binfmt_misc can currently only be mounted in the initial user namespace, binary types registered in this binfmt_misc instance are available to all sandboxes (Either by having them installed in the sandbox or by registering the binary type with the F flag causing the interpreter to be opened right away). So binfmt_misc binary types are already delegated to sandboxes implicitly. However, while a sandbox has access to all registered binary types in binfmt_misc a sandbox cannot currently register its own binary types in binfmt_misc. This has prevented various use-cases some of which were already outlined in [1] but we have a range of issues associated with this (cf. [3]-[5] below which are just a small sample). Extend binfmt_misc to be mountable in non-initial user namespaces. Similar to other filesystem such as nfsd, mqueue, and sunrpc we use keyed superblock management. The key determines whether we need to create a new superblock or can reuse an already existing one. We use the user namespace of the mount as key. This means a new binfmt_misc superblock is created once per user namespace creation. Subsequent mounts of binfmt_misc in the same user namespace will mount the same binfmt_misc instance. We explicitly do not create a new binfmt_misc superblock on every binfmt_misc mount as the semantics for load_misc_binary() line up with the keying model. This also allows us to retrieve the relevant binfmt_misc instance based on the caller's user namespace which can be done in a simple (bounded to 32 levels) loop. Similar to the current binfmt_misc semantics allowing access to the binary types in the initial binfmt_misc instance we do allow sandboxes access to their parent's binfmt_misc mounts if they do not have created a separate binfmt_misc instance. Overall, this will unblock the use-cases mentioned below and in general will also allow to support and harden execution of another architecture's binaries in tight sandboxes. For instance, using the unshare binary it possible to start a chroot of another architecture and configure the binfmt_misc interpreter without being root to run the binaries in this chroot and without requiring the host to modify its binary type handlers. Henning had already posted a few experiments in the cover letter at [1]. But here's an additional example where an unprivileged container registers qemu-user-static binary handlers for various binary types in its separate binfmt_misc mount and is then seamlessly able to start containers with a different architecture without affecting the host: root [lxc monitor] /var/snap/lxd/common/lxd/containers f1 1000000 \_ /sbin/init 1000000 \_ /lib/systemd/systemd-journald 1000000 \_ /lib/systemd/systemd-udevd 1000100 \_ /lib/systemd/systemd-networkd 1000101 \_ /lib/systemd/systemd-resolved 1000000 \_ /usr/sbin/cron -f 1000103 \_ /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only 1000000 \_ /usr/bin/python3 /usr/bin/networkd-dispatcher --run-startup-triggers 1000104 \_ /usr/sbin/rsyslogd -n -iNONE 1000000 \_ /lib/systemd/systemd-logind 1000000 \_ /sbin/agetty -o -p -- \u --noclear --keep-baud console 115200,38400,9600 vt220 1000107 \_ dnsmasq --conf-file=/dev/null -u lxc-dnsmasq --strict-order --bind-interfaces --pid-file=/run/lxc/dnsmasq.pid --liste 1000000 \_ [lxc monitor] /var/lib/lxc f1-s390x 1100000 \_ /usr/bin/qemu-s390x-static /sbin/init 1100000 \_ /usr/bin/qemu-s390x-static /lib/systemd/systemd-journald 1100000 \_ /usr/bin/qemu-s390x-static /usr/sbin/cron -f 1100103 \_ /usr/bin/qemu-s390x-static /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-ac 1100000 \_ /usr/bin/qemu-s390x-static /usr/bin/python3 /usr/bin/networkd-dispatcher --run-startup-triggers 1100104 \_ /usr/bin/qemu-s390x-static /usr/sbin/rsyslogd -n -iNONE 1100000 \_ /usr/bin/qemu-s390x-static /lib/systemd/systemd-logind 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud console 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/0 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/1 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/2 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/3 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /lib/systemd/systemd-udevd [1]: https://lore.kernel.org/all/20191216091220.465626-1-laurent@vivier.eu [2]: https://discuss.linuxcontainers.org/t/binfmt-misc-permission-denied [3]: https://discuss.linuxcontainers.org/t/lxd-binfmt-support-for-qemu-static-interpreters [4]: https://discuss.linuxcontainers.org/t/3-1-0-binfmt-support-service-in-unprivileged-guest-requires-write-access-on-hosts-proc-sys-fs-binfmt-misc [5]: https://discuss.linuxcontainers.org/t/qemu-user-static-not-working-4-11 Link: https://lore.kernel.org/r/20191216091220.465626-2-laurent@vivier.eu (origin) Link: https://lore.kernel.org/r/20211028103114.2849140-2-brauner@kernel.org (v1) Cc: Sargun Dhillon <sargun@sargun.me> Cc: Serge Hallyn <serge@hallyn.com> Cc: Jann Horn <jannh@google.com> Cc: Henning Schild <henning.schild@siemens.com> Cc: Andrei Vagin <avagin@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Laurent Vivier <laurent@vivier.eu> Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Laurent Vivier <laurent@vivier.eu> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> --- /* v2 */ - Serge Hallyn <serge@hallyn.com>: - Use GFP_KERNEL_ACCOUNT for userspace triggered allocations when a new binary type handler is registered. - Christian Brauner <christian.brauner@ubuntu.com>: - Switch authorship to me. I refused to do that earlier even though Laurent said I should do so because I think it's genuinely bad form. But by now I have changed so many things that it'd be unfair to blame Laurent for any potential bugs in here. - Add more comments that explain what's going on. - Rename functions while changing them to better reflect what they are doing to make the code easier to understand. - In the first version when a specific binary type handler was removed either through a write to the entry's file or all binary type handlers were removed by a write to the binfmt_misc mount's status file all cleanup work happened during inode eviction. That includes removal of the relevant entries from entry list. While that works fine I disliked that model after thinking about it for a bit. Because it means that there was a window were someone has already removed a or all binary handlers but they could still be safely reached from load_misc_binary() when it has managed to take the read_lock() on the entries list while inode eviction was already happening. Again, that perfectly benign but it's cleaner to remove the binary handler from the list immediately meaning that ones the write to then entry's file or the binfmt_misc status file returns the binary type cannot be executed anymore. That gives stronger guarantees to the user.
2022-09-30binfmt: remove taso from linux_binprm structLukas Bulwahn1-3/+0
With commit 987f20a9dcce ("a.out: Remove the a.out implementation"), the use of the special taso flag for alpha architectures in the linux_binprm struct is gone. Remove the definition of taso in the linux_binprm struct. No functional change. Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220929203903.9475-1-lukas.bulwahn@gmail.com
2022-03-08coredump: Move definition of struct coredump_params into coredump.hEric W. Biederman1-12/+1
Move the definition of struct coredump_params into coredump.h where it belongs. Remove the slightly errorneous comment explaining why struct coredump_params was declared in binfmts.h. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2022-03-02binfmt: move more stuff undef CONFIG_COREDUMPAlexey Dobriyan1-0/+2
struct linux_binfmt::core_dump and struct min_coredump::min_coredump are used under CONFIG_COREDUMP only. Shrink those embedded configs a bit. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/YglbIFyN+OtwVyjW@localhost.localdomain
2021-03-08coredump: don't bother with do_truncate()Al Viro1-0/+1
have dump_skip() just remember how much needs to be skipped, leave actual seeks/writing zeroes to the next dump_emit() or the end of coredump output, whichever comes first. And instead of playing with do_truncate() in the end, just write one NUL at the end of the last gap (if any). Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2021-02-15binfmt_misc: pass binfmt_misc flags to the interpreterLaurent Vivier1-0/+4
It can be useful to the interpreter to know which flags are in use. For instance, knowing if the preserve-argv[0] is in use would allow to skip the pathname argument. This patch uses an unused auxiliary vector, AT_FLAGS, to add a flag to inform interpreter if the preserve-argv[0] is enabled. Note by Helge Deller: The real-world user of this patch is qemu-user, which needs to know if it has to preserve the argv[0]. See Debian bug #970460. Signed-off-by: Laurent Vivier <laurent@vivier.eu> Reviewed-by: YunQiang Su <ysu@wavecomp.com> URL: http://bugs.debian.org/970460 Signed-off-by: Helge Deller <deller@gmx.de>
2020-07-21exec: Implement kernel_execveEric W. Biederman1-7/+2
To allow the kernel not to play games with set_fs to call exec implement kernel_execve. The function kernel_execve takes pointers into kernel memory and copies the values pointed to onto the new userspace stack. The calls with arguments from kernel space of do_execve are replaced with calls to kernel_execve. The calls do_execve and do_execveat are made static as there are now no callers outside of exec. The comments that mention do_execve are updated to refer to kernel_execve or execve depending on the circumstances. In addition to correcting the comments, this makes it easy to grep for do_execve and verify it is not used. Inspired-by: https://lkml.kernel.org/r/20200627072704.2447163-1-hch@lst.de Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/87wo365ikj.fsf@x220.int.ebiederm.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-07-21exec: Move initialization of bprm->filename into alloc_bprmEric W. Biederman1-0/+1
Currently it is necessary for the usermode helper code and the code that launches init to use set_fs so that pages coming from the kernel look like they are coming from userspace. To allow that usage of set_fs to be removed cleanly the argument copying from userspace needs to happen earlier. Move the computation of bprm->filename and possible allocation of a name in the case of execveat into alloc_bprm to make that possible. The exectuable name, the arguments, and the environment are copied into the new usermode stack which is stored in bprm until exec passes the point of no return. As the executable name is copied first onto the usermode stack it needs to be known. As there are no dependencies to computing the executable name, compute it early in alloc_bprm. As an implementation detail if the filename needs to be generated because it embeds a file descriptor store that filename in a new field bprm->fdpath, and free it in free_bprm. Previously this was done in an independent variable pathbuf. I have renamed pathbuf fdpath because fdpath is more suggestive of what kind of path is in the variable. I moved fdpath into struct linux_binprm because it is tightly tied to the other variables in struct linux_binprm, and as such is needed to allow the call alloc_binprm to move. Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lkml.kernel.org/r/87k0z66x8f.fsf@x220.int.ebiederm.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-07-21exec: Remove unnecessary spaces from binfmts.hEric W. Biederman1-5/+5
The general convention in the linux kernel is to define a pointer member as "type *name". The declaration of struct linux_binprm has several pointer defined as "type * name". Update them to the form of "type *name" for consistency. Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lkml.kernel.org/r/87v9iq6x9x.fsf@x220.int.ebiederm.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-07-04exec: Remove do_execve_fileEric W. Biederman1-1/+0
Now that the last callser has been removed remove this code from exec. For anyone thinking of resurrecing do_execve_file please note that the code was buggy in several fundamental ways. - It did not ensure the file it was passed was read-only and that deny_write_access had been called on it. Which subtlely breaks invaniants in exec. - The caller of do_execve_file was expected to hold and put a reference to the file, but an extra reference for use by exec was not taken so that when exec put it's reference to the file an underflow occured on the file reference count. - The point of the interface was so that a pathname did not need to exist. Which breaks pathname based LSMs. Tetsuo Handa originally reported these issues[1]. While it was clear that deny_write_access was missing the fundamental incompatibility with the passed in O_RDWR filehandle was not immediately recognized. All of these issues were fixed by modifying the usermode driver code to have a path, so it did not need this hack. Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> [1] https://lore.kernel.org/linux-fsdevel/2a8775b4-1dd5-9d5c-aa42-9872445e0942@i-love.sakura.ne.jp/ v1: https://lkml.kernel.org/r/871rm2f0hi.fsf_-_@x220.int.ebiederm.org v2: https://lkml.kernel.org/r/87lfk54p0m.fsf_-_@x220.int.ebiederm.org Link: https://lkml.kernel.org/r/20200702164140.4468-10-ebiederm@xmission.com Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Alexei Starovoitov <ast@kernel.org> Tested-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-06-05Merge branch 'akpm' (patches from Andrew)Linus Torvalds1-2/+1
Merge yet more updates from Andrew Morton: - More MM work. 100ish more to go. Mike Rapoport's "mm: remove __ARCH_HAS_5LEVEL_HACK" series should fix the current ppc issue - Various other little subsystems * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (127 commits) lib/ubsan.c: fix gcc-10 warnings tools/testing/selftests/vm: remove duplicate headers selftests: vm: pkeys: fix multilib builds for x86 selftests: vm: pkeys: use the correct page size on powerpc selftests/vm/pkeys: override access right definitions on powerpc selftests/vm/pkeys: test correct behaviour of pkey-0 selftests/vm/pkeys: introduce a sub-page allocator selftests/vm/pkeys: detect write violation on a mapped access-denied-key page selftests/vm/pkeys: associate key on a mapped page and detect write violation selftests/vm/pkeys: associate key on a mapped page and detect access violation selftests/vm/pkeys: improve checks to determine pkey support selftests/vm/pkeys: fix assertion in test_pkey_alloc_exhaust() selftests/vm/pkeys: fix number of reserved powerpc pkeys selftests/vm/pkeys: introduce powerpc support selftests/vm/pkeys: introduce generic pkey abstractions selftests: vm: pkeys: use the correct huge page size selftests/vm/pkeys: fix alloc_random_pkey() to make it really random selftests/vm/pkeys: fix assertion in pkey_disable_set/clear() selftests/vm/pkeys: fix pkey_disable_clear() selftests: vm: pkeys: add helpers for pkey bits ...
2020-06-05exec: simplify the copy_strings_kernel calling conventionChristoph Hellwig1-2/+1
copy_strings_kernel is always used with a single argument, adjust the calling convention to that. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Link: http://lkml.kernel.org/r/20200501104105.2621149-2-hch@lst.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-30exec: Compute file based creds only onceEric W. Biederman1-12/+2
Move the computation of creds from prepare_binfmt into begin_new_exec so that the creds need only be computed once. This is just code reorganization no semantic changes of any kind are made. Moving the computation is safe. I have looked through the kernel and verified none of the binfmts look at bprm->cred directly, and that there are no helpers that look at bprm->cred indirectly. Which means that it is not a problem to compute the bprm->cred later in the execution flow as it is not used until it becomes current->cred. A new function bprm_creds_from_file is added to contain the work that needs to be done. bprm_creds_from_file first computes which file bprm->executable or most likely bprm->file that the bprm->creds will be computed from. The funciton bprm_fill_uid is updated to receive the file instead of accessing bprm->file. The now unnecessary work needed to reset the bprm->cred->euid, and bprm->cred->egid is removed from brpm_fill_uid. A small comment to document that bprm_fill_uid now only deals with the work to handle suid and sgid files. The default case is already heandled by prepare_exec_creds. The function security_bprm_repopulate_creds is renamed security_bprm_creds_from_file and now is explicitly passed the file from which to compute the creds. The documentation of the bprm_creds_from_file security hook is updated to explain when the hook is called and what it needs to do. The file is passed from cap_bprm_creds_from_file into get_file_caps so that the caps are computed for the appropriate file. The now unnecessary work in cap_bprm_creds_from_file to reset the ambient capabilites has been removed. A small comment to document that the work of cap_bprm_creds_from_file is to read capabilities from the files secureity attribute and derive capabilities from the fact the user had uid 0 has been added. Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-30exec: Add a per bprm->file version of per_clearEric W. Biederman1-0/+5
There is a small bug in the code that recomputes parts of bprm->cred for every bprm->file. The code never recomputes the part of clear_dangerous_personality_flags it is responsible for. Which means that in practice if someone creates a sgid script the interpreter will not be able to use any of: READ_IMPLIES_EXEC ADDR_NO_RANDOMIZE ADDR_COMPAT_LAYOUT MMAP_PAGE_ZERO. This accentially clearing of personality flags probably does not matter in practice because no one has complained but it does make the code more difficult to understand. Further remaining bug compatible prevents the recomputation from being removed and replaced by simply computing bprm->cred once from the final bprm->file. Making this change removes the last behavior difference between computing bprm->creds from the final file and recomputing bprm->cred several times. Which allows this behavior change to be justified for it's own reasons, and for any but hunts looking into why the behavior changed to wind up here instead of in the code that will follow that computes bprm->cred from the final bprm->file. This small logic bug appears to have existed since the code started clearing dangerous personality bits. History Tree: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Fixes: 1bb0fa189c6a ("[PATCH] NX: clean up legacy binary support") Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-21exec: Remove recursion from search_binary_handlerEric W. Biederman1-2/+1
Recursion in kernel code is generally a bad idea as it can overflow the kernel stack. Recursion in exec also hides that the code is looping and that the loop changes bprm->file. Instead of recursing in search_binary_handler have the methods that would recurse set bprm->interpreter and return 0. Modify exec_binprm to loop when bprm->interpreter is set. Consolidate all of the reassignments of bprm->file in that loop to make it clear what is going on. The structure of the new loop in exec_binprm is that all errors return immediately, while successful completion (ret == 0 && !bprm->interpreter) just breaks out of the loop and runs what exec_bprm has always run upon successful completion. Fail if the an interpreter is being call after execfd has been set. The code has never properly handled an interpreter being called with execfd being set and with reassignments of bprm->file and the assignment of bprm->executable in generic code it has finally become possible to test and fail when if this problematic condition happens. With the reassignments of bprm->file and the assignment of bprm->executable moved into the generic code add a test to see if bprm->executable is being reassigned. In search_binary_handler remove the test for !bprm->file. With all reassignments of bprm->file moved to exec_binprm bprm->file can never be NULL in search_binary_handler. Link: https://lkml.kernel.org/r/87sgfwyd84.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-21exec: Generic execfd supportEric W. Biederman1-5/+5
Most of the support for passing the file descriptor of an executable to an interpreter already lives in the generic code and in binfmt_elf. Rework the fields in binfmt_elf that deal with executable file descriptor passing to make executable file descriptor passing a first class concept. Move the fd_install from binfmt_misc into begin_new_exec after the new creds have been installed. This means that accessing the file through /proc/<pid>/fd/N is able to see the creds for the new executable before allowing access to the new executables files. Performing the install of the executables file descriptor after the point of no return also means that nothing special needs to be done on error. The exiting of the process will close all of it's open files. Move the would_dump from binfmt_misc into begin_new_exec right after would_dump is called on the bprm->file. This makes it obvious this case exists and that no nesting of bprm->file is currently supported. In binfmt_misc the movement of fd_install into generic code means that it's special error exit path is no longer needed. Link: https://lkml.kernel.org/r/87y2poyd91.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-21exec: Move the call of prepare_binprm into search_binary_handlerEric W. Biederman1-1/+0
The code in prepare_binary_handler needs to be run every time search_binary_handler is called so move the call into search_binary_handler itself to make the code simpler and easier to understand. Link: https://lkml.kernel.org/r/87d070zrvx.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-21exec: Allow load_misc_binary to call prepare_binprm unconditionallyEric W. Biederman1-0/+2
Add a flag preserve_creds that binfmt_misc can set to prevent credentials from being updated. This allows binfmt_misc to always call prepare_binprm. Allowing the credential computation logic to be consolidated. Not replacing the credentials with the interpreters credentials is safe because because an open file descriptor to the executable is passed to the interpreter. As the interpreter does not need to reopen the executable it is guaranteed to see the same file that exec sees. Ref: c407c033de84 ("[PATCH] binfmt_misc: improve calculation of interpreter's credentials") Link: https://lkml.kernel.org/r/87imgszrwo.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-21exec: Convert security_bprm_set_creds into security_bprm_repopulate_credsEric W. Biederman1-2/+2
Rename bprm->cap_elevated to bprm->active_secureexec and initialize it in prepare_binprm instead of in cap_bprm_set_creds. Initializing bprm->active_secureexec in prepare_binprm allows multiple implementations of security_bprm_repopulate_creds to play nicely with each other. Rename security_bprm_set_creds to security_bprm_reopulate_creds to emphasize that this path recomputes part of bprm->cred. This recomputation avoids the time of check vs time of use problems that are inherent in unix #! interpreters. In short two renames and a move in the location of initializing bprm->active_secureexec. Link: https://lkml.kernel.org/r/87o8qkzrxp.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-20exec: Factor security_bprm_creds_for_exec out of security_bprm_set_credsEric W. Biederman1-13/+5
Today security_bprm_set_creds has several implementations: apparmor_bprm_set_creds, cap_bprm_set_creds, selinux_bprm_set_creds, smack_bprm_set_creds, and tomoyo_bprm_set_creds. Except for cap_bprm_set_creds they all test bprm->called_set_creds and return immediately if it is true. The function cap_bprm_set_creds ignores bprm->calld_sed_creds entirely. Create a new LSM hook security_bprm_creds_for_exec that is called just before prepare_binprm in __do_execve_file, resulting in a LSM hook that is called exactly once for the entire of exec. Modify the bits of security_bprm_set_creds that only want to be called once per exec into security_bprm_creds_for_exec, leaving only cap_bprm_set_creds behind. Remove bprm->called_set_creds all of it's former users have been moved to security_bprm_creds_for_exec. Add or upate comments a appropriate to bring them up to date and to reflect this change. Link: https://lkml.kernel.org/r/87v9kszrzh.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Casey Schaufler <casey@schaufler-ca.com> # For the LSM and Smack bits Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-08exec: Rename flush_old_exec begin_new_execEric W. Biederman1-1/+1
There is and has been for a very long time been a lot more going on in flush_old_exec than just flushing the old state. After the movement of code from setup_new_exec there is a whole lot more going on than just flushing the old executables state. Rename flush_old_exec to begin_new_exec to more accurately reflect what this function does. Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Greg Ungerer <gerg@linux-m68k.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-08exec: Merge install_exec_creds into setup_new_execEric W. Biederman1-1/+0
The two functions are now always called one right after the other so merge them together to make future maintenance easier. Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Greg Ungerer <gerg@linux-m68k.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-08exec: Rename the flag called_exec_mmap point_of_no_returnEric W. Biederman1-3/+3
Update the comments and make the code easier to understand by renaming this flag. Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Greg Ungerer <gerg@linux-m68k.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-05-08exec: Make unlocking exec_update_mutex explictEric W. Biederman1-2/+1
With install_exec_creds updated to follow immediately after setup_new_exec, the failure of unshare_sighand is the only code path where exec_update_mutex is held but not explicitly unlocked. Update that code path to explicitly unlock exec_update_mutex. Remove the unlocking of exec_update_mutex from free_bprm. Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Greg Ungerer <gerg@linux-m68k.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-03-25exec: Add exec_update_mutex to replace cred_guard_mutexEric W. Biederman1-1/+7
The cred_guard_mutex is problematic as it is held over possibly indefinite waits for userspace. The possible indefinite waits for userspace that I have identified are: The cred_guard_mutex is held in PTRACE_EVENT_EXIT waiting for the tracer. The cred_guard_mutex is held over "put_user(0, tsk->clear_child_tid)" in exit_mm(). The cred_guard_mutex is held over "get_user(futex_offset, ...") in exit_robust_list. The cred_guard_mutex held over copy_strings. The functions get_user and put_user can trigger a page fault which can potentially wait indefinitely in the case of userfaultfd or if userspace implements part of the page fault path. In any of those cases the userspace process that the kernel is waiting for might make a different system call that winds up taking the cred_guard_mutex and result in deadlock. Holding a mutex over any of those possibly indefinite waits for userspace does not appear necessary. Add exec_update_mutex that will just cover updating the process during exec where the permissions and the objects pointed to by the task struct may be out of sync. The plan is to switch the users of cred_guard_mutex to exec_update_mutex one by one. This lets us move forward while still being careful and not introducing any regressions. Link: https://lore.kernel.org/lkml/20160921152946.GA24210@dhcp22.suse.cz/ Link: https://lore.kernel.org/lkml/AM6PR03MB5170B06F3A2B75EFB98D071AE4E60@AM6PR03MB5170.eurprd03.prod.outlook.com/ Link: https://lore.kernel.org/linux-fsdevel/20161102181806.GB1112@redhat.com/ Link: https://lore.kernel.org/lkml/20160923095031.GA14923@redhat.com/ Link: https://lore.kernel.org/lkml/20170213141452.GA30203@redhat.com/ Ref: 45c1a159b85b ("Add PTRACE_O_TRACEVFORKDONE and PTRACE_O_TRACEEXIT facilities.") Ref: 456f17cd1a28 ("[PATCH] user-vm-unlock-2.5.31-A2") Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2019-05-15exec: move struct linux_binprm::bufAlexey Dobriyan1-1/+2
struct linux_binprm::buf is the first field and it is exactly 128 bytes in size. It means that on x86_64 all accesses to other fields will go though [r64 + disp32] addressing mode which is 3 bytes bloatier than [r64 + disp8] addressing mode. Given that accesses to other fields outnumber accesses to ->buf, move it down. Space savings (x86_64 defconfig): more on distro configs because LSMs actively dereference "bprm" but do not care about first 128 bytes of the executable itself. add/remove: 0/0 grow/shrink: 0/24 up/down: 0/-492 (-492) Function old new delta selinux_bprm_committing_creds 552 549 -3 finalize_exec 94 91 -3 __audit_log_bprm_fcaps 283 280 -3 __audit_bprm 39 36 -3 perf_trace_sched_process_exec 347 341 -6 install_exec_creds 105 99 -6 cap_bprm_set_creds.cold 60 54 -6 would_dump 137 128 -9 load_script 637 628 -9 bprm_change_interp 61 52 -9 trace_event_raw_event_sched_process_exec 260 250 -10 search_binary_handler 255 240 -15 remove_arg_zero 295 277 -18 free_bprm 119 101 -18 prepare_binprm 379 360 -19 setup_new_exec 336 315 -21 flush_old_exec 1638 1617 -21 copy_strings.isra 746 724 -22 setup_arg_pages 559 530 -29 load_misc_binary 1151 1118 -33 selinux_bprm_set_creds 792 753 -39 load_elf_binary 11111 11072 -39 cap_bprm_set_creds 1496 1454 -42 __do_execve_file.isra 2395 2286 -109 Link: http://lkml.kernel.org/r/20190421165025.GA26843@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-06Merge branch 'for-linus' of ↵Linus Torvalds1-1/+0
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull trivial vfs updates from Al Viro: "A few cleanups + Neil's namespace_unlock() optimization" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: exec: make prepare_bprm_creds static genheaders: %-<width>s had been there since v6; %-*s - since v7 VFS: use synchronize_rcu_expedited() in namespace_unlock() iov_iter: reduce code duplication
2019-01-05exec: separate MM_ANONPAGES and RLIMIT_STACK accountingOleg Nesterov1-0/+1
get_arg_page() checks bprm->rlim_stack.rlim_cur and re-calculates the "extra" size for argv/envp pointers every time, this is a bit ugly and even not strictly correct: acct_arg_size() must not account this size. Remove all the rlimit code in get_arg_page(). Instead, add bprm->argmin calculated once at the start of __do_execve_file() and change copy_strings to check bprm->p >= bprm->argmin. The patch adds the new helper, prepare_arg_pages() which initializes bprm->argc/envc and bprm->argmin. [oleg@redhat.com: fix !CONFIG_MMU version of get_arg_page()] Link: http://lkml.kernel.org/r/20181126122307.GA1660@redhat.com [akpm@linux-foundation.org: use max_t] Link: http://lkml.kernel.org/r/20181112160910.GA28440@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Tested-by: Guenter Roeck <linux@roeck-us.net> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-12-10exec: make prepare_bprm_creds staticChanho Min1-1/+0
prepare_bprm_creds is not used outside exec.c, so there's no reason for it to have external linkage. Signed-off-by: Chanho Min <chanho.min@lge.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-10-03signal: Distinguish between kernel_siginfo and siginfoEric W. Biederman1-1/+1
Linus recently observed that if we did not worry about the padding member in struct siginfo it is only about 48 bytes, and 48 bytes is much nicer than 128 bytes for allocating on the stack and copying around in the kernel. The obvious thing of only adding the padding when userspace is including siginfo.h won't work as there are sigframe definitions in the kernel that embed struct siginfo. So split siginfo in two; kernel_siginfo and siginfo. Keeping the traditional name for the userspace definition. While the version that is used internally to the kernel and ultimately will not be padded to 128 bytes is called kernel_siginfo. The definition of struct kernel_siginfo I have put in include/signal_types.h A set of buildtime checks has been added to verify the two structures have the same field offsets. To make it easy to verify the change kernel_siginfo retains the same size as siginfo. The reduction in size comes in a following change. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-05-23umh: introduce fork_usermode_blob() helperAlexei Starovoitov1-0/+1
Introduce helper: int fork_usermode_blob(void *data, size_t len, struct umh_info *info); struct umh_info { struct file *pipe_to_umh; struct file *pipe_from_umh; pid_t pid; }; that GPLed kernel modules (signed or unsigned) can use it to execute part of its own data as swappable user mode process. The kernel will do: - allocate a unique file in tmpfs - populate that file with [data, data + len] bytes - user-mode-helper code will do_execve that file and, before the process starts, the kernel will create two unix pipes for bidirectional communication between kernel module and umh - close tmpfs file, effectively deleting it - the fork_usermode_blob will return zero on success and populate 'struct umh_info' with two unix pipes and the pid of the user process As the first step in the development of the bpfilter project the fork_usermode_blob() helper is introduced to allow user mode code to be invoked from a kernel module. The idea is that user mode code plus normal kernel module code are built as part of the kernel build and installed as traditional kernel module into distro specified location, such that from a distribution point of view, there is no difference between regular kernel modules and kernel modules + umh code. Such modules can be signed, modprobed, rmmod, etc. The use of this new helper by a kernel module doesn't make it any special from kernel and user space tooling point of view. Such approach enables kernel to delegate functionality traditionally done by the kernel modules into the user space processes (either root or !root) and reduces security attack surface of the new code. The buggy umh code would crash the user process, but not the kernel. Another advantage is that umh code of the kernel module can be debugged and tested out of user space (e.g. opening the possibility to run clang sanitizers, fuzzers or user space test suites on the umh code). In case of the bpfilter project such architecture allows complex control plane to be done in the user space while bpf based data plane stays in the kernel. Since umh can crash, can be oom-ed by the kernel, killed by the admin, the kernel module that uses them (like bpfilter) needs to manage life time of umh on its own via two unix pipes and the pid of umh. The exit code of such kernel module should kill the umh it started, so that rmmod of the kernel module will cleanup the corresponding umh. Just like if the kernel module does kmalloc() it should kfree() it in the exit code. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2018-04-11exec: pin stack limit during execKees Cook1-0/+2
Since the stack rlimit is used in multiple places during exec and it can be changed via other threads (via setrlimit()) or processes (via prlimit()), the assumption that the value doesn't change cannot be made. This leads to races with mm layout selection and argument size calculations. This changes the exec path to use the rlimit stored in bprm instead of in current. Before starting the thread, the bprm stack rlimit is stored back to current. Link: http://lkml.kernel.org/r/1518638796-20819-4-git-send-email-keescook@chromium.org Fixes: 64701dee4178e ("exec: Use sane stack rlimit under secureexec") Signed-off-by: Kees Cook <keescook@chromium.org> Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Reported-by: Andy Lutomirski <luto@kernel.org> Reported-by: Brad Spengler <spender@grsecurity.net> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Greg KH <greg@kroah.com> Cc: Hugh Dickins <hughd@google.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Laura Abbott <labbott@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Willy Tarreau <w@1wt.eu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11exec: introduce finalize_exec() before start_thread()Kees Cook1-0/+1
Provide a final callback into fs/exec.c before start_thread() takes over, to handle any last-minute changes, like the coming restoration of the stack limit. Link: http://lkml.kernel.org/r/1518638796-20819-3-git-send-email-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Ben Hutchings <ben.hutchings@codethink.co.uk> Cc: Brad Spengler <spender@grsecurity.net> Cc: Greg KH <greg@kroah.com> Cc: Hugh Dickins <hughd@google.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Laura Abbott <labbott@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Willy Tarreau <w@1wt.eu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-02License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman1-0/+1
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-10-04exec: load_script: kill the onstack interp[BINPRM_BUF_SIZE] arrayOleg Nesterov1-1/+1
Patch series "exec: binfmt_misc: fix use-after-free, kill iname[BINPRM_BUF_SIZE]". It looks like this code was always wrong, then commit 948b701a607f ("binfmt_misc: add persistent opened binary handler for containers") added more problems. This patch (of 6): load_script() can simply use i_name instead, it points into bprm->buf[] and nobody can change this memory until we call prepare_binprm(). The only complication is that we need to also change the signature of bprm_change_interp() but this change looks good too. While at it, do whitespace/style cleanups. NOTE: the real motivation for this change is that people want to increase BINPRM_BUF_SIZE, we need to change load_misc_binary() too but this looks more complicated because afaics it is very buggy. Link: http://lkml.kernel.org/r/20170918163446.GA26793@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Travis Gummels <tgummels@redhat.com> Cc: Ben Woodard <woodard@redhat.com> Cc: Jim Foraker <foraker1@llnl.gov> Cc: <tdhooge@llnl.gov> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-08-01commoncap: Move cap_elevated calculation into bprm_set_credsKees Cook1-3/+0
Instead of a separate function, open-code the cap_elevated test, which lets us entirely remove bprm->cap_effective (to use the local "effective" variable instead), and more accurately examine euid/egid changes via the existing local "is_setid". The following LTP tests were run to validate the changes: # ./runltp -f syscalls -s cap # ./runltp -f securebits # ./runltp -f cap_bounds # ./runltp -f filecaps All kernel selftests for capabilities and exec continue to pass as well. Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: James Morris <james.l.morris@oracle.com> Acked-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Andy Lutomirski <luto@kernel.org>
2017-08-01commoncap: Refactor to remove bprm_secureexec hookKees Cook1-0/+7
The commoncap implementation of the bprm_secureexec hook is the only LSM that depends on the final call to its bprm_set_creds hook (since it may be called for multiple files, it ignores bprm->called_set_creds). As a result, it cannot safely _clear_ bprm->secureexec since other LSMs may have set it. Instead, remove the bprm_secureexec hook by introducing a new flag to bprm specific to commoncap: cap_elevated. This is similar to cap_effective, but that is used for a specific subset of elevated privileges, and exists solely to track state from bprm_set_creds to bprm_secureexec. As such, it will be removed in the next patch. Here, set the new bprm->cap_elevated flag when setuid/setgid has happened from bprm_fill_uid() or fscapabilities have been prepared. This temporarily moves the bprm_secureexec hook to a static inline. The helper will be removed in the next patch; this makes the step easier to review and bisect, since this does not introduce any changes to inputs nor outputs to the "elevated privileges" calculation. The new flag is merged with the bprm->secureexec flag in setup_new_exec() since this marks the end of any further prepare_binprm() calls. Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Andy Lutomirski <luto@kernel.org> Acked-by: James Morris <james.l.morris@oracle.com> Acked-by: Serge Hallyn <serge@hallyn.com>
2017-08-01binfmt: Introduce secureexec flagKees Cook1-1/+7
The bprm_secureexec hook can be moved earlier. Right now, it is called during create_elf_tables(), via load_binary(), via search_binary_handler(), via exec_binprm(). Nearly all (see exception below) state used by bprm_secureexec is created during the bprm_set_creds hook, called from prepare_binprm(). For all LSMs (except commoncaps described next), only the first execution of bprm_set_creds takes any effect (they all check bprm->called_set_creds which prepare_binprm() sets after the first call to the bprm_set_creds hook). However, all these LSMs also only do anything with bprm_secureexec when they detected a secure state during their first run of bprm_set_creds. Therefore, it is functionally identical to move the detection into bprm_set_creds, since the results from secureexec here only need to be based on the first call to the LSM's bprm_set_creds hook. The single exception is that the commoncaps secureexec hook also examines euid/uid and egid/gid differences which are controlled by bprm_fill_uid(), via prepare_binprm(), which can be called multiple times (e.g. binfmt_script, binfmt_misc), and may clear the euid/egid for the final load (i.e. the script interpreter). However, while commoncaps specifically ignores bprm->cred_prepared, and runs its bprm_set_creds hook each time prepare_binprm() may get called, it needs to base the secureexec decision on the final call to bprm_set_creds. As a result, it will need special handling. To begin this refactoring, this adds the secureexec flag to the bprm struct, and calls the secureexec hook during setup_new_exec(). This is safe since all the cred work is finished (and past the point of no return). This explicit call will be removed in later patches once the hook has been removed. Cc: David Howells <dhowells@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: John Johansen <john.johansen@canonical.com> Acked-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: James Morris <james.l.morris@oracle.com>
2017-08-01exec: Rename bprm->cred_prepared to called_set_credsKees Cook1-2/+6
The cred_prepared bprm flag has a misleading name. It has nothing to do with the bprm_prepare_cred hook, and actually tracks if bprm_set_creds has been called. Rename this flag and improve its comment. Cc: David Howells <dhowells@redhat.com> Cc: Stephen Smalley <sds@tycho.nsa.gov> Cc: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: John Johansen <john.johansen@canonical.com> Acked-by: James Morris <james.l.morris@oracle.com> Acked-by: Paul Moore <paul@paul-moore.com> Acked-by: Serge Hallyn <serge@hallyn.com>
2017-06-30randstruct: Mark various structs for randomizationKees Cook1-2/+2
This marks many critical kernel structures for randomization. These are structures that have been targeted in the past in security exploits, or contain functions pointers, pointers to function pointer tables, lists, workqueues, ref-counters, credentials, permissions, or are otherwise sensitive. This initial list was extracted from Brad Spengler/PaX Team's code in the last public patch of grsecurity/PaX based on my understanding of the code. Changes or omissions from the original code are mine and don't reflect the original grsecurity/PaX code. Left out of this list is task_struct, which requires special handling and will be covered in a subsequent patch. Signed-off-by: Kees Cook <keescook@chromium.org>
2017-03-03sched/headers, vfs/execve: Move the do_execve*() prototypes from ↵Ingo Molnar1-0/+10
<linux/sched.h> to <linux/binfmts.h> These are not scheduler related. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-25elf_fdpic_transfer_args_to_stack(): make it genericNicolas Pitre1-0/+2
This copying of arguments and environment is common to both NOMMU binary formats we support. Let's make the elf_fdpic version available to the flat format as well. While at it, improve the code a bit not to copy below the actual data area. Signed-off-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Greg Ungerer <gerg@linux-m68k.org> Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
2016-06-08coredump: fix dumping through pipesMateusz Guzik1-0/+1
The offset in the core file used to be tracked with ->written field of the coredump_params structure. The field was retired in favour of file->f_pos. However, ->f_pos is not maintained for pipes which leads to breakage. Restore explicit tracking of the offset in coredump_params. Introduce ->pos field for this purpose since ->written was already reused. Fixes: a00839395103 ("get rid of coredump_params->written"). Reported-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> Signed-off-by: Mateusz Guzik <mguzik@redhat.com> Reviewed-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-12-13syscalls: implement execveat() system callDavid Drysdale1-0/+4
This patchset adds execveat(2) for x86, and is derived from Meredydd Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528). The primary aim of adding an execveat syscall is to allow an implementation of fexecve(3) that does not rely on the /proc filesystem, at least for executables (rather than scripts). The current glibc version of fexecve(3) is implemented via /proc, which causes problems in sandboxed or otherwise restricted environments. Given the desire for a /proc-free fexecve() implementation, HPA suggested (https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be an appropriate generalization. Also, having a new syscall means that it can take a flags argument without back-compatibility concerns. The current implementation just defines the AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be added in future -- for example, flags for new namespaces (as suggested at https://lkml.org/lkml/2006/7/11/474). Related history: - https://lkml.org/lkml/2006/12/27/123 is an example of someone realizing that fexecve() is likely to fail in a chroot environment. - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered documenting the /proc requirement of fexecve(3) in its manpage, to "prevent other people from wasting their time". - https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a problem where a process that did setuid() could not fexecve() because it no longer had access to /proc/self/fd; this has since been fixed. This patch (of 4): Add a new execveat(2) system call. execveat() is to execve() as openat() is to open(): it takes a file descriptor that refers to a directory, and resolves the filename relative to that. In addition, if the filename is empty and AT_EMPTY_PATH is specified, execveat() executes the file to which the file descriptor refers. This replicates the functionality of fexecve(), which is a system call in other UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and so relies on /proc being mounted). The filename fed to the executed program as argv[0] (or the name of the script fed to a script interpreter) will be of the form "/dev/fd/<fd>" (for an empty filename) or "/dev/fd/<fd>/<filename>", effectively reflecting how the executable was found. This does however mean that execution of a script in a /proc-less environment won't work; also, script execution via an O_CLOEXEC file descriptor fails (as the file will not be accessible after exec). Based on patches by Meredydd Luff. Signed-off-by: David Drysdale <drysdale@google.com> Cc: Meredydd Luff <meredydd@senatehouse.org> Cc: Shuah Khan <shuah.kh@samsung.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Rich Felker <dalias@aerifal.cx> Cc: Christoph Hellwig <hch@infradead.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08exec: kill bprm->tcomm[], simplify the "basename" logicOleg Nesterov1-1/+0
Starting from commit c4ad8f98bef7 ("execve: use 'struct filename *' for executable name passing") bprm->filename can not go away after flush_old_exec(), so we do not need to save the binary name in bprm->tcomm[] added by 96e02d158678 ("exec: fix use-after-free bug in setup_new_exec()"). And there was never need for filename_to_taskname-like code, we can simply do set_task_comm(kbasename(filename). This patch has to change set_task_comm() and trace_task_rename() to accept "const char *", but I think this change is also good. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-02-06execve: use 'struct filename *' for executable name passingLinus Torvalds1-1/+0
This changes 'do_execve()' to get the executable name as a 'struct filename', and to free it when it is done. This is what the normal users want, and it simplifies and streamlines their error handling. The controlled lifetime of the executable name also fixes a use-after-free problem with the trace_sched_process_exec tracepoint: the lifetime of the passed-in string for kernel users was not at all obvious, and the user-mode helper code used UMH_WAIT_EXEC to serialize the pathname allocation lifetime with the execve() having finished, which in turn meant that the trace point that happened after mm_release() of the old process VM ended up using already free'd memory. To solve the kernel string lifetime issue, this simply introduces "getname_kernel()" that works like the normal user-space getname() function, except with the source coming from kernel memory. As Oleg points out, this also means that we could drop the tcomm[] array from 'struct linux_binprm', since the pathname lifetime now covers setup_new_exec(). That would be a separate cleanup. Reported-by: Igor Zhbanov <i.zhbanov@samsung.com> Tested-by: Steven Rostedt <rostedt@goodmis.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-11-13Merge branch 'akpm' (patches from Andrew Morton)Linus Torvalds1-3/+0
Merge first patch-bomb from Andrew Morton: "Quite a lot of other stuff is banked up awaiting further next->mainline merging, but this batch contains: - Lots of random misc patches - OCFS2 - Most of MM - backlight updates - lib/ updates - printk updates - checkpatch updates - epoll tweaking - rtc updates - hfs - hfsplus - documentation - procfs - update gcov to gcc-4.7 format - IPC" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (269 commits) ipc, msg: fix message length check for negative values ipc/util.c: remove unnecessary work pending test devpts: plug the memory leak in kill_sb ./Makefile: export initial ramdisk compression config option init/Kconfig: add option to disable kernel compression drivers: w1: make w1_slave::flags long to avoid memory corruption drivers/w1/masters/ds1wm.cuse dev_get_platdata() drivers/memstick/core/ms_block.c: fix unreachable state in h_msb_read_page() drivers/memstick/core/mspro_block.c: fix attributes array allocation drivers/pps/clients/pps-gpio.c: remove redundant of_match_ptr kernel/panic.c: reduce 1 byte usage for print tainted buffer gcov: reuse kbasename helper kernel/gcov/fs.c: use pr_warn() kernel/module.c: use pr_foo() gcov: compile specific gcov implementation based on gcc version gcov: add support for gcc 4.7 gcov format gcov: move gcov structs definitions to a gcc version specific file kernel/taskstats.c: return -ENOMEM when alloc memory fails in add_del_listener() kernel/taskstats.c: add nla_nest_cancel() for failure processing between nla_nest_start() and nla_nest_end() kernel/sysctl_binary.c: use scnprintf() instead of snprintf() ...
2013-11-13exec/ptrace: fix get_dumpable() incorrect testsKees Cook1-3/+0
The get_dumpable() return value is not boolean. Most users of the function actually want to be testing for non-SUID_DUMP_USER(1) rather than SUID_DUMP_DISABLE(0). The SUID_DUMP_ROOT(2) is also considered a protected state. Almost all places did this correctly, excepting the two places fixed in this patch. Wrong logic: if (dumpable == SUID_DUMP_DISABLE) { /* be protective */ } or if (dumpable == 0) { /* be protective */ } or if (!dumpable) { /* be protective */ } Correct logic: if (dumpable != SUID_DUMP_USER) { /* be protective */ } or if (dumpable != 1) { /* be protective */ } Without this patch, if the system had set the sysctl fs/suid_dumpable=2, a user was able to ptrace attach to processes that had dropped privileges to that user. (This may have been partially mitigated if Yama was enabled.) The macros have been moved into the file that declares get/set_dumpable(), which means things like the ia64 code can see them too. CVE-2013-2929 Reported-by: Vasily Kulikov <segoon@openwall.com> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-11-09constify do_coredump() argumentAl Viro1-1/+1
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-11-09new helper: dump_emit()Al Viro1-0/+1
dump_write() analog, takes core_dump_params instead of file, keeps track of the amount written in cprm->written and checks for cprm->limit. Start using it in binfmt_elf.c... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>