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2020-08-12exec: move S_ISREG() check earlierKees Cook1-6/+0
The execve(2)/uselib(2) syscalls have always rejected non-regular files. Recently, it was noticed that a deadlock was introduced when trying to execute pipes, as the S_ISREG() test was happening too late. This was fixed in commit 73601ea5b7b1 ("fs/open.c: allow opening only regular files during execve()"), but it was added after inode_permission() had already run, which meant LSMs could see bogus attempts to execute non-regular files. Move the test into the other inode type checks (which already look for other pathological conditions[1]). Since there is no need to use FMODE_EXEC while we still have access to "acc_mode", also switch the test to MAY_EXEC. Also include a comment with the redundant S_ISREG() checks at the end of execve(2)/uselib(2) to note that they are present to avoid any mistakes. My notes on the call path, and related arguments, checks, etc: do_open_execat() struct open_flags open_exec_flags = { .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, .acc_mode = MAY_EXEC, ... do_filp_open(dfd, filename, open_flags) path_openat(nameidata, open_flags, flags) file = alloc_empty_file(open_flags, current_cred()); do_open(nameidata, file, open_flags) may_open(path, acc_mode, open_flag) /* new location of MAY_EXEC vs S_ISREG() test */ inode_permission(inode, MAY_OPEN | acc_mode) security_inode_permission(inode, acc_mode) vfs_open(path, file) do_dentry_open(file, path->dentry->d_inode, open) /* old location of FMODE_EXEC vs S_ISREG() test */ security_file_open(f) open() [1] https://lore.kernel.org/lkml/202006041910.9EF0C602@keescook/ Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Eric Biggers <ebiggers3@gmail.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Link: http://lkml.kernel.org/r/20200605160013.3954297-3-keescook@chromium.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-07Merge branch 'hch.init_path' of ↵Linus Torvalds1-39/+39
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull init and set_fs() cleanups from Al Viro: "Christoph's 'getting rid of ksys_...() uses under KERNEL_DS' series" * 'hch.init_path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (50 commits) init: add an init_dup helper init: add an init_utimes helper init: add an init_stat helper init: add an init_mknod helper init: add an init_mkdir helper init: add an init_symlink helper init: add an init_link helper init: add an init_eaccess helper init: add an init_chmod helper init: add an init_chown helper init: add an init_chroot helper init: add an init_chdir helper init: add an init_rmdir helper init: add an init_unlink helper init: add an init_umount helper init: add an init_mount helper init: mark create_dev as __init init: mark console_on_rootfs as __init init: initialize ramdisk_execute_command at compile time devtmpfs: refactor devtmpfsd() ...
2020-07-31init: add an init_eaccess helperChristoph Hellwig1-1/+1
Add a simple helper to check if a file exists based on kernel space file name and switch the early init code over to it. Note that this theoretically changes behavior as it always is based on the effective permissions. But during early init that doesn't make a difference. Signed-off-by: Christoph Hellwig <hch@lst.de>
2020-07-31init: add an init_chmod helperChristoph Hellwig1-2/+2
Add a simple helper to chmod with a kernel space file name and switch the early init code over to it. Signed-off-by: Christoph Hellwig <hch@lst.de>
2020-07-31init: add an init_chown helperChristoph Hellwig1-1/+1
Add a simple helper to chown with a kernel space file name and switch the early init code over to it. Signed-off-by: Christoph Hellwig <hch@lst.de>
2020-07-31init: add an init_chroot helperChristoph Hellwig1-6/+1
Add a simple helper to chroot with a kernel space file name and switch the early init code over to it. Remove the now unused ksys_chroot. Signed-off-by: Christoph Hellwig <hch@lst.de>
2020-07-31init: add an init_chdir helperChristoph Hellwig1-6/+1
Add a simple helper to chdir with a kernel space file name and switch the early init code over to it. Remove the now unused ksys_chdir. Signed-off-by: Christoph Hellwig <hch@lst.de>
2020-07-31fs: remove ksys_fchmodChristoph Hellwig1-6/+1
Fold it into the only remaining caller. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-07-31fs: remove ksys_openChristoph Hellwig1-3/+8
Just open code it in the two callers. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-07-16fs: add a vfs_fchmod helperChristoph Hellwig1-2/+7
Add a helper for struct file based chmode operations. To be used by the initramfs code soon. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-07-16fs: add a vfs_fchown helperChristoph Hellwig1-12/+17
Add a helper for struct file based chown operations. To be used by the initramfs code soon. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-17close_range: add CLOSE_RANGE_UNSHAREChristian Brauner1-4/+1
One of the use-cases of close_range() is to drop file descriptors just before execve(). This would usually be expressed in the sequence: unshare(CLONE_FILES); close_range(3, ~0U); as pointed out by Linus it might be desirable to have this be a part of close_range() itself under a new flag CLOSE_RANGE_UNSHARE. This expands {dup,unshare)_fd() to take a max_fds argument that indicates the maximum number of file descriptors to copy from the old struct files. When the user requests that all file descriptors are supposed to be closed via close_range(min, max) then we can cap via unshare_fd(min) and hence don't need to do any of the heavy fput() work for everything above min. The patch makes it so that if CLOSE_RANGE_UNSHARE is requested and we do in fact currently share our file descriptor table we create a new private copy. We then close all fds in the requested range and finally after we're done we install the new fd table. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-06-17open: add close_range()Christian Brauner1-0/+20
This adds the close_range() syscall. It allows to efficiently close a range of file descriptors up to all file descriptors of a calling task. I was contacted by FreeBSD as they wanted to have the same close_range() syscall as we proposed here. We've coordinated this and in the meantime, Kyle was fast enough to merge close_range() into FreeBSD already in April: https://reviews.freebsd.org/D21627 https://svnweb.freebsd.org/base?view=revision&revision=359836 and the current plan is to backport close_range() to FreeBSD 12.2 (cf. [2]) once its merged in Linux too. Python is in the process of switching to close_range() on FreeBSD and they are waiting on us to merge this to switch on Linux as well: https://bugs.python.org/issue38061 The syscall came up in a recent discussion around the new mount API and making new file descriptor types cloexec by default. During this discussion, Al suggested the close_range() syscall (cf. [1]). Note, a syscall in this manner has been requested by various people over time. First, it helps to close all file descriptors of an exec()ing task. This can be done safely via (quoting Al's example from [1] verbatim): /* that exec is sensitive */ unshare(CLONE_FILES); /* we don't want anything past stderr here */ close_range(3, ~0U); execve(....); The code snippet above is one way of working around the problem that file descriptors are not cloexec by default. This is aggravated by the fact that we can't just switch them over without massively regressing userspace. For a whole class of programs having an in-kernel method of closing all file descriptors is very helpful (e.g. demons, service managers, programming language standard libraries, container managers etc.). (Please note, unshare(CLONE_FILES) should only be needed if the calling task is multi-threaded and shares the file descriptor table with another thread in which case two threads could race with one thread allocating file descriptors and the other one closing them via close_range(). For the general case close_range() before the execve() is sufficient.) Second, it allows userspace to avoid implementing closing all file descriptors by parsing through /proc/<pid>/fd/* and calling close() on each file descriptor. From looking at various large(ish) userspace code bases this or similar patterns are very common in: - service managers (cf. [4]) - libcs (cf. [6]) - container runtimes (cf. [5]) - programming language runtimes/standard libraries - Python (cf. [2]) - Rust (cf. [7], [8]) As Dmitry pointed out there's even a long-standing glibc bug about missing kernel support for this task (cf. [3]). In addition, the syscall will also work for tasks that do not have procfs mounted and on kernels that do not have procfs support compiled in. In such situations the only way to make sure that all file descriptors are closed is to call close() on each file descriptor up to UINT_MAX or RLIMIT_NOFILE, OPEN_MAX trickery (cf. comment [8] on Rust). The performance is striking. For good measure, comparing the following simple close_all_fds() userspace implementation that is essentially just glibc's version in [6]: static int close_all_fds(void) { int dir_fd; DIR *dir; struct dirent *direntp; dir = opendir("/proc/self/fd"); if (!dir) return -1; dir_fd = dirfd(dir); while ((direntp = readdir(dir))) { int fd; if (strcmp(direntp->d_name, ".") == 0) continue; if (strcmp(direntp->d_name, "..") == 0) continue; fd = atoi(direntp->d_name); if (fd == dir_fd || fd == 0 || fd == 1 || fd == 2) continue; close(fd); } closedir(dir); return 0; } to close_range() yields: 1. closing 4 open files: - close_all_fds(): ~280 us - close_range(): ~24 us 2. closing 1000 open files: - close_all_fds(): ~5000 us - close_range(): ~800 us close_range() is designed to allow for some flexibility. Specifically, it does not simply always close all open file descriptors of a task. Instead, callers can specify an upper bound. This is e.g. useful for scenarios where specific file descriptors are created with well-known numbers that are supposed to be excluded from getting closed. For extra paranoia close_range() comes with a flags argument. This can e.g. be used to implement extension. Once can imagine userspace wanting to stop at the first error instead of ignoring errors under certain circumstances. There might be other valid ideas in the future. In any case, a flag argument doesn't hurt and keeps us on the safe side. From an implementation side this is kept rather dumb. It saw some input from David and Jann but all nonsense is obviously my own! - Errors to close file descriptors are currently ignored. (Could be changed by setting a flag in the future if needed.) - __close_range() is a rather simplistic wrapper around __close_fd(). My reasoning behind this is based on the nature of how __close_fd() needs to release an fd. But maybe I misunderstood specifics: We take the files_lock and rcu-dereference the fdtable of the calling task, we find the entry in the fdtable, get the file and need to release files_lock before calling filp_close(). In the meantime the fdtable might have been altered so we can't just retake the spinlock and keep the old rcu-reference of the fdtable around. Instead we need to grab a fresh reference to the fdtable. If my reasoning is correct then there's really no point in fancyfying __close_range(): We just need to rcu-dereference the fdtable of the calling task once to cap the max_fd value correctly and then go on calling __close_fd() in a loop. /* References */ [1]: https://lore.kernel.org/lkml/20190516165021.GD17978@ZenIV.linux.org.uk/ [2]: https://github.com/python/cpython/blob/9e4f2f3a6b8ee995c365e86d976937c141d867f8/Modules/_posixsubprocess.c#L220 [3]: https://sourceware.org/bugzilla/show_bug.cgi?id=10353#c7 [4]: https://github.com/systemd/systemd/blob/5238e9575906297608ff802a27e2ff9effa3b338/src/basic/fd-util.c#L217 [5]: https://github.com/lxc/lxc/blob/ddf4b77e11a4d08f09b7b9cd13e593f8c047edc5/src/lxc/start.c#L236 [6]: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/grantpt.c;h=2030e07fa6e652aac32c775b8c6e005844c3c4eb;hb=HEAD#l17 Note that this is an internal implementation that is not exported. Currently, libc seems to not provide an exported version of this because of missing kernel support to do this. Note, in a recent patch series Florian made grantpt() a nop thereby removing the code referenced here. [7]: https://github.com/rust-lang/rust/issues/12148 [8]: https://github.com/rust-lang/rust/blob/5f47c0613ed4eb46fca3633c1297364c09e5e451/src/libstd/sys/unix/process2.rs#L303-L308 Rust's solution is slightly different but is equally unperformant. Rust calls getdtablesize() which is a glibc library function that simply returns the current RLIMIT_NOFILE or OPEN_MAX values. Rust then goes on to call close() on each fd. That's obviously overkill for most tasks. Rarely, tasks - especially non-demons - hit RLIMIT_NOFILE or OPEN_MAX. Let's be nice and assume an unprivileged user with RLIMIT_NOFILE set to 1024. Even in this case, there's a very high chance that in the common case Rust is calling the close() syscall 1021 times pointlessly if the task just has 0, 1, and 2 open. Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Kyle Evans <self@kyle-evans.net> Cc: Jann Horn <jannh@google.com> Cc: David Howells <dhowells@redhat.com> Cc: Dmitry V. Levin <ldv@altlinux.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: linux-api@vger.kernel.org
2020-06-02Merge branch 'akpm' (patches from Andrew)Linus Torvalds1-2/+1
Merge updates from Andrew Morton: "A few little subsystems and a start of a lot of MM patches. Subsystems affected by this patch series: squashfs, ocfs2, parisc, vfs. With mm subsystems: slab-generic, slub, debug, pagecache, gup, swap, memcg, pagemap, memory-failure, vmalloc, kasan" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (128 commits) kasan: move kasan_report() into report.c mm/mm_init.c: report kasan-tag information stored in page->flags ubsan: entirely disable alignment checks under UBSAN_TRAP kasan: fix clang compilation warning due to stack protector x86/mm: remove vmalloc faulting mm: remove vmalloc_sync_(un)mappings() x86/mm/32: implement arch_sync_kernel_mappings() x86/mm/64: implement arch_sync_kernel_mappings() mm/ioremap: track which page-table levels were modified mm/vmalloc: track which page-table levels were modified mm: add functions to track page directory modifications s390: use __vmalloc_node in stack_alloc powerpc: use __vmalloc_node in alloc_vm_stack arm64: use __vmalloc_node in arch_alloc_vmap_stack mm: remove vmalloc_user_node_flags mm: switch the test_vmalloc module to use __vmalloc_node mm: remove __vmalloc_node_flags_caller mm: remove both instances of __vmalloc_node_flags mm: remove the prot argument to __vmalloc_node mm: remove the pgprot argument to __vmalloc ...
2020-06-02vfs: track per-sb writeback errors and report them to syncfsJeff Layton1-2/+1
Patch series "vfs: have syncfs() return error when there are writeback errors", v6. Currently, syncfs does not return errors when one of the inodes fails to be written back. It will return errors based on the legacy AS_EIO and AS_ENOSPC flags when syncing out the block device fails, but that's not particularly helpful for filesystems that aren't backed by a blockdev. It's also possible for a stray sync to lose those errors. The basic idea in this set is to track writeback errors at the superblock level, so that we can quickly and easily check whether something bad happened without having to fsync each file individually. syncfs is then changed to reliably report writeback errors after they occur, much in the same fashion as fsync does now. This patch (of 2): Usually we suggest that applications call fsync when they want to ensure that all data written to the file has made it to the backing store, but that can be inefficient when there are a lot of open files. Calling syncfs on the filesystem can be more efficient in some situations, but the error reporting doesn't currently work the way most people expect. If a single inode on a filesystem reports a writeback error, syncfs won't necessarily return an error. syncfs only returns an error if __sync_blockdev fails, and on some filesystems that's a no-op. It would be better if syncfs reported an error if there were any writeback failures. Then applications could call syncfs to see if there are any errors on any open files, and could then call fsync on all of the other descriptors to figure out which one failed. This patch adds a new errseq_t to struct super_block, and has mapping_set_error also record writeback errors there. To report those errors, we also need to keep an errseq_t in struct file to act as a cursor. This patch adds a dedicated field for that purpose, which slots nicely into 4 bytes of padding at the end of struct file on x86_64. An earlier version of this patch used an O_PATH file descriptor to cue the kernel that the open file should track the superblock error and not the inode's writeback error. I think that API is just too weird though. This is simpler and should make syncfs error reporting "just work" even if someone is multiplexing fsync and syncfs on the same fds. Signed-off-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Andres Freund <andres@anarazel.de> Cc: Matthew Wilcox <willy@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: David Howells <dhowells@redhat.com> Link: http://lkml.kernel.org/r/20200428135155.19223-1-jlayton@kernel.org Link: http://lkml.kernel.org/r/20200428135155.19223-2-jlayton@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-14vfs: add faccessat2 syscallMiklos Szeredi1-8/+26
POSIX defines faccessat() as having a fourth "flags" argument, while the linux syscall doesn't have it. Glibc tries to emulate AT_EACCESS and AT_SYMLINK_NOFOLLOW, but AT_EACCESS emulation is broken. Add a new faccessat(2) syscall with the added flags argument and implement both flags. The value of AT_EACCESS is defined in glibc headers to be the same as AT_REMOVEDIR. Use this value for the kernel interface as well, together with the explanatory comment. Also add AT_EMPTY_PATH support, which is not documented by POSIX, but can be useful and is trivial to implement. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-05-14vfs: split out access_override_creds()Miklos Szeredi1-10/+24
Split out a helper that overrides the credentials in preparation for actually doing the access check. This prepares for the next patch that optionally disables the creds override. Suggested-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-04-02Merge branch 'work.dotdot1' of ↵Linus Torvalds1-1/+3
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs pathwalk sanitizing from Al Viro: "Massive pathwalk rewrite and cleanups. Several iterations have been posted; hopefully this thing is getting readable and understandable now. Pretty much all parts of pathname resolutions are affected... The branch is identical to what has sat in -next, except for commit message in "lift all calls of step_into() out of follow_dotdot/ follow_dotdot_rcu", crediting Qian Cai for reporting the bug; only commit message changed there." * 'work.dotdot1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (69 commits) lookup_open(): don't bother with fallbacks to lookup+create atomic_open(): no need to pass struct open_flags anymore open_last_lookups(): move complete_walk() into do_open() open_last_lookups(): lift O_EXCL|O_CREAT handling into do_open() open_last_lookups(): don't abuse complete_walk() when all we want is unlazy open_last_lookups(): consolidate fsnotify_create() calls take post-lookup part of do_last() out of loop link_path_walk(): sample parent's i_uid and i_mode for the last component __nd_alloc_stack(): make it return bool reserve_stack(): switch to __nd_alloc_stack() pick_link(): take reserving space on stack into a new helper pick_link(): more straightforward handling of allocation failures fold path_to_nameidata() into its only remaining caller pick_link(): pass it struct path already with normal refcounting rules fs/namei.c: kill follow_mount() non-RCU analogue of the previous commit helper for mount rootwards traversal follow_dotdot(): be lazy about changing nd->path follow_dotdot_rcu(): be lazy about changing nd->path follow_dotdot{,_rcu}(): massage loops ...
2020-03-13cifs_atomic_open(): fix double-put on late allocation failureAl Viro1-3/+0
several iterations of ->atomic_open() calling conventions ago, we used to need fput() if ->atomic_open() failed at some point after successful finish_open(). Now (since 2016) it's not needed - struct file carries enough state to make fput() work regardless of the point in struct file lifecycle and discarding it on failure exits in open() got unified. Unfortunately, I'd missed the fact that we had an instance of ->atomic_open() (cifs one) that used to need that fput(), as well as the stale comment in finish_open() demanding such late failure handling. Trivially fixed... Fixes: fe9ec8291fca "do_last(): take fput() on error after opening to out:" Cc: stable@kernel.org # v4.7+ Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2020-02-27make build_open_flags() treat O_CREAT | O_EXCL as implying O_NOFOLLOWAl Viro1-1/+3
O_CREAT | O_EXCL means "-EEXIST if we run into a trailing symlink". As it is, we might or might not have LOOKUP_FOLLOW in op->intent in that case - that depends upon having O_NOFOLLOW in open flags. It doesn't matter, since we won't be checking it in that case - do_last() bails out earlier. However, making sure it's not set (i.e. acting as if we had an explicit O_NOFOLLOW) makes the behaviour more explicit and allows to reorder the check for O_CREAT | O_EXCL in do_last() with the call of step_into() immediately following it. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2020-01-21fs: make build_open_flags() available internallyJens Axboe1-3/+2
This is a prep patch for supporting non-blocking open from io_uring. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-01-18open: introduce openat2(2) syscallAleksa Sarai1-34/+113
/* Background. */ For a very long time, extending openat(2) with new features has been incredibly frustrating. This stems from the fact that openat(2) is possibly the most famous counter-example to the mantra "don't silently accept garbage from userspace" -- it doesn't check whether unknown flags are present[1]. This means that (generally) the addition of new flags to openat(2) has been fraught with backwards-compatibility issues (O_TMPFILE has to be defined as __O_TMPFILE|O_DIRECTORY|[O_RDWR or O_WRONLY] to ensure old kernels gave errors, since it's insecure to silently ignore the flag[2]). All new security-related flags therefore have a tough road to being added to openat(2). Userspace also has a hard time figuring out whether a particular flag is supported on a particular kernel. While it is now possible with contemporary kernels (thanks to [3]), older kernels will expose unknown flag bits through fcntl(F_GETFL). Giving a clear -EINVAL during openat(2) time matches modern syscall designs and is far more fool-proof. In addition, the newly-added path resolution restriction LOOKUP flags (which we would like to expose to user-space) don't feel related to the pre-existing O_* flag set -- they affect all components of path lookup. We'd therefore like to add a new flag argument. Adding a new syscall allows us to finally fix the flag-ignoring problem, and we can make it extensible enough so that we will hopefully never need an openat3(2). /* Syscall Prototype. */ /* * open_how is an extensible structure (similar in interface to * clone3(2) or sched_setattr(2)). The size parameter must be set to * sizeof(struct open_how), to allow for future extensions. All future * extensions will be appended to open_how, with their zero value * acting as a no-op default. */ struct open_how { /* ... */ }; int openat2(int dfd, const char *pathname, struct open_how *how, size_t size); /* Description. */ The initial version of 'struct open_how' contains the following fields: flags Used to specify openat(2)-style flags. However, any unknown flag bits or otherwise incorrect flag combinations (like O_PATH|O_RDWR) will result in -EINVAL. In addition, this field is 64-bits wide to allow for more O_ flags than currently permitted with openat(2). mode The file mode for O_CREAT or O_TMPFILE. Must be set to zero if flags does not contain O_CREAT or O_TMPFILE. resolve Restrict path resolution (in contrast to O_* flags they affect all path components). The current set of flags are as follows (at the moment, all of the RESOLVE_ flags are implemented as just passing the corresponding LOOKUP_ flag). RESOLVE_NO_XDEV => LOOKUP_NO_XDEV RESOLVE_NO_SYMLINKS => LOOKUP_NO_SYMLINKS RESOLVE_NO_MAGICLINKS => LOOKUP_NO_MAGICLINKS RESOLVE_BENEATH => LOOKUP_BENEATH RESOLVE_IN_ROOT => LOOKUP_IN_ROOT open_how does not contain an embedded size field, because it is of little benefit (userspace can figure out the kernel open_how size at runtime fairly easily without it). It also only contains u64s (even though ->mode arguably should be a u16) to avoid having padding fields which are never used in the future. Note that as a result of the new how->flags handling, O_PATH|O_TMPFILE is no longer permitted for openat(2). As far as I can tell, this has always been a bug and appears to not be used by userspace (and I've not seen any problems on my machines by disallowing it). If it turns out this breaks something, we can special-case it and only permit it for openat(2) but not openat2(2). After input from Florian Weimer, the new open_how and flag definitions are inside a separate header from uapi/linux/fcntl.h, to avoid problems that glibc has with importing that header. /* Testing. */ In a follow-up patch there are over 200 selftests which ensure that this syscall has the correct semantics and will correctly handle several attack scenarios. In addition, I've written a userspace library[4] which provides convenient wrappers around openat2(RESOLVE_IN_ROOT) (this is necessary because no other syscalls support RESOLVE_IN_ROOT, and thus lots of care must be taken when using RESOLVE_IN_ROOT'd file descriptors with other syscalls). During the development of this patch, I've run numerous verification tests using libpathrs (showing that the API is reasonably usable by userspace). /* Future Work. */ Additional RESOLVE_ flags have been suggested during the review period. These can be easily implemented separately (such as blocking auto-mount during resolution). Furthermore, there are some other proposed changes to the openat(2) interface (the most obvious example is magic-link hardening[5]) which would be a good opportunity to add a way for userspace to restrict how O_PATH file descriptors can be re-opened. Another possible avenue of future work would be some kind of CHECK_FIELDS[6] flag which causes the kernel to indicate to userspace which openat2(2) flags and fields are supported by the current kernel (to avoid userspace having to go through several guesses to figure it out). [1]: https://lwn.net/Articles/588444/ [2]: https://lore.kernel.org/lkml/CA+55aFyyxJL1LyXZeBsf2ypriraj5ut1XkNDsunRBqgVjZU_6Q@mail.gmail.com [3]: commit 629e014bb834 ("fs: completely ignore unknown open flags") [4]: https://sourceware.org/bugzilla/show_bug.cgi?id=17523 [5]: https://lore.kernel.org/lkml/20190930183316.10190-2-cyphar@cyphar.com/ [6]: https://youtu.be/ggD-eb3yPVs Suggested-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-11-26Revert "vfs: properly and reliably lock f_pos in fdget_pos()"Linus Torvalds1-1/+5
This reverts commit 0be0ee71816b2b6725e2b4f32ad6726c9d729777. I was hoping it would be benign to switch over entirely to FMODE_STREAM, and we'd have just a couple of small fixups we'd need, but it looks like we're not quite there yet. While it worked fine on both my desktop and laptop, they are fairly similar in other respects, and run mostly the same loads. Kenneth Crudup reports that it seems to break both his vmware installation and the KDE upower service. In both cases apparently leading to timeouts due to waitinmg for the f_pos lock. There are a number of character devices in particular that definitely want stream-like behavior, but that currently don't get marked as streams, and as a result get the exclusion between concurrent read()/write() on the same file descriptor. Which doesn't work well for them. The most obvious example if this is /dev/console and /dev/tty, which use console_fops and tty_fops respectively (and ptmx_fops for the pty master side). It may be that it's just this that causes problems, but we clearly weren't ready yet. Because there's a number of other likely common cases that don't have llseek implementations and would seem to act as stream devices: /dev/fuse (fuse_dev_operations) /dev/mcelog (mce_chrdev_ops) /dev/mei0 (mei_fops) /dev/net/tun (tun_fops) /dev/nvme0 (nvme_dev_fops) /dev/tpm0 (tpm_fops) /proc/self/ns/mnt (ns_file_operations) /dev/snd/pcm* (snd_pcm_f_ops[]) and while some of these could be trivially automatically detected by the vfs layer when the character device is opened by just noticing that they have no read or write operations either, it often isn't that obvious. Some character devices most definitely do use the file position, even if they don't allow seeking: the firmware update code, for example, uses simple_read_from_buffer() that does use f_pos, but doesn't allow seeking back and forth. We'll revisit this when there's a better way to detect the problem and fix it (possibly with a coccinelle script to do more of the FMODE_STREAM annotations). Reported-by: Kenneth R. Crudup <kenny@panix.com> Cc: Kirill Smelkov <kirr@nexedi.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-11-25vfs: properly and reliably lock f_pos in fdget_pos()Linus Torvalds1-5/+1
fdget_pos() is used by file operations that will read and update f_pos: things like "read()", "write()" and "lseek()" (but not, for example, "pread()/pwrite" that get their file positions elsewhere). However, it had two separate escape clauses for this, because not everybody wants or needs serialization of the file position. The first and most obvious case is the "file descriptor doesn't have a position at all", ie a stream-like file. Except we didn't actually use FMODE_STREAM, but instead used FMODE_ATOMIC_POS. The reason for that was that FMODE_STREAM didn't exist back in the days, but also that we didn't want to mark all the special cases, so we only marked the ones that _required_ position atomicity according to POSIX - regular files and directories. The case one was intentionally lazy, but now that we _do_ have FMODE_STREAM we could and should just use it. With the change to use FMODE_STREAM, there are no remaining uses for FMODE_ATOMIC_POS, and all the code to set it is deleted. Any cases where we don't want the serialization because the driver (or subsystem) doesn't use the file position should just be updated to do "stream_open()". We've done that for all the obvious and common situations, we may need a few more. Quoting Kirill Smelkov in the original FMODE_STREAM thread (see link below for full email): "And I appreciate if people could help at least somehow with "getting rid of mixed case entirely" (i.e. always lock f_pos_lock on !FMODE_STREAM), because this transition starts to diverge from my particular use-case too far. To me it makes sense to do that transition as follows: - convert nonseekable_open -> stream_open via stream_open.cocci; - audit other nonseekable_open calls and convert left users that truly don't depend on position to stream_open; - extend stream_open.cocci to analyze alloc_file_pseudo as well (this will cover pipes and sockets), or maybe convert pipes and sockets to FMODE_STREAM manually; - extend stream_open.cocci to analyze file_operations that use no_llseek or noop_llseek, but do not use nonseekable_open or alloc_file_pseudo. This might find files that have stream semantic but are opened differently; - extend stream_open.cocci to analyze file_operations whose .read/.write do not use ppos at all (independently of how file was opened); - ... - after that remove FMODE_ATOMIC_POS and always take f_pos_lock if !FMODE_STREAM; - gather bug reports for deadlocked read/write and convert missed cases to FMODE_STREAM, probably extending stream_open.cocci along the road to catch similar cases i.e. always take f_pos_lock unless a file is explicitly marked as being stream, and try to find and cover all files that are streams" We have not done the "extend stream_open.cocci to analyze alloc_file_pseudo" as well, but the previous commit did manually handle the case of pipes and sockets. The other case where we can avoid locking f_pos is the "this file descriptor only has a single user and it is us, and thus there is no need to lock it". The second test was correct, although a bit subtle and worth just re-iterating here. There are two kinds of other sources of references to the same file descriptor: file descriptors that have been explicitly shared across fork() or with dup(), and file tables having elevated reference counts due to threading (or explicit file sharing with clone()). The first case would have incremented the file count explicitly, and in the second case the previous __fdget() would have incremented it for us and set the FDPUT_FPUT flag. But in both cases the file count would be greater than one, so the "file_count(file) > 1" test catches both situations. Also note that if file_count is 1, that also means that no other thread can have access to the file table, so there also cannot be races with concurrent calls to dup()/fork()/clone() that would increment the file count any other way. Link: https://lore.kernel.org/linux-fsdevel/20190413184404.GA13490@deco.navytux.spb.ru Cc: Kirill Smelkov <kirr@nexedi.com> Cc: Eic Dumazet <edumazet@google.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Marco Elver <elver@google.com> Cc: Andrea Parri <parri.andrea@gmail.com> Cc: Paul McKenney <paulmck@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-09-26fs: remove unlikely() from WARN_ON() conditionDenis Efremov1-1/+1
"unlikely(WARN_ON(x))" is excessive. WARN_ON() already uses unlikely() internally. Link: http://lkml.kernel.org/r/20190829165025.15750-5-efremov@linux.com Signed-off-by: Denis Efremov <efremov@linux.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-09-25mm,thp: avoid writes to file with THP in pagecacheSong Liu1-0/+8
In previous patch, an application could put part of its text section in THP via madvise(). These THPs will be protected from writes when the application is still running (TXTBSY). However, after the application exits, the file is available for writes. This patch avoids writes to file THP by dropping page cache for the file when the file is open for write. A new counter nr_thps is added to struct address_space. In do_dentry_open(), if the file is open for write and nr_thps is non-zero, we drop page cache for the whole file. Link: http://lkml.kernel.org/r/20190801184244.3169074-8-songliubraving@fb.com Signed-off-by: Song Liu <songliubraving@fb.com> Reported-by: kbuild test robot <lkp@intel.com> Acked-by: Rik van Riel <riel@surriel.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Hillf Danton <hdanton@sina.com> Cc: Hugh Dickins <hughd@google.com> Cc: William Kucharski <william.kucharski@oracle.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-24access: avoid the RCU grace period for the temporary subjective credentialsLinus Torvalds1-0/+19
It turns out that 'access()' (and 'faccessat()') can cause a lot of RCU work because it installs a temporary credential that gets allocated and freed for each system call. The allocation and freeing overhead is mostly benign, but because credentials can be accessed under the RCU read lock, the freeing involves a RCU grace period. Which is not a huge deal normally, but if you have a lot of access() calls, this causes a fair amount of seconday damage: instead of having a nice alloc/free patterns that hits in hot per-CPU slab caches, you have all those delayed free's, and on big machines with hundreds of cores, the RCU overhead can end up being enormous. But it turns out that all of this is entirely unnecessary. Exactly because access() only installs the credential as the thread-local subjective credential, the temporary cred pointer doesn't actually need to be RCU free'd at all. Once we're done using it, we can just free it synchronously and avoid all the RCU overhead. So add a 'non_rcu' flag to 'struct cred', which can be set by users that know they only use it in non-RCU context (there are other potential users for this). We can make it a union with the rcu freeing list head that we need for the RCU case, so this doesn't need any extra storage. Note that this also makes 'get_current_cred()' clear the new non_rcu flag, in case we have filesystems that take a long-term reference to the cred and then expect the RCU delayed freeing afterwards. It's not entirely clear that this is required, but it makes for clear semantics: the subjective cred remains non-RCU as long as you only access it synchronously using the thread-local accessors, but you _can_ use it as a generic cred if you want to. It is possible that we should just remove the whole RCU markings for ->cred entirely. Only ->real_cred is really supposed to be accessed through RCU, and the long-term cred copies that nfs uses might want to explicitly re-enable RCU freeing if required, rather than have get_current_cred() do it implicitly. But this is a "minimal semantic changes" change for the immediate problem. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Eric Dumazet <edumazet@google.com> Acked-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Jan Glauber <jglauber@marvell.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Jayachandran Chandrasekharan Nair <jnair@marvell.com> Cc: Greg KH <greg@kroah.com> Cc: Kees Cook <keescook@chromium.org> Cc: David Howells <dhowells@redhat.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-05-21treewide: Add SPDX license identifier for missed filesThomas Gleixner1-0/+1
Add SPDX license identifiers to all files which: - Have no license information of any form - Have EXPORT_.*_SYMBOL_GPL inside which was used in the initial scan/conversion to ignore the file These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-06vfs: pass ppos=NULL to .read()/.write() of FMODE_STREAM filesKirill Smelkov1-2/+3
This amends commit 10dce8af3422 ("fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock") in how position is passed into .read()/.write() handler for stream-like files: Rasmus noticed that we currently pass 0 as position and ignore any position change if that is done by a file implementation. This papers over bugs if ppos is used in files that declare themselves as being stream-like as such bugs will go unnoticed. Even if a file implementation is correctly converted into using stream_open, its read/write later could be changed to use ppos and even though that won't be working correctly, that bug might go unnoticed without someone doing wrong behaviour analysis. It is thus better to pass ppos=NULL into read/write for stream-like files as that don't give any chance for ppos usage bugs because it will oops if ppos is ever used inside .read() or .write(). Note 1: rw_verify_area, new_sync_{read,write} needs to be updated because they are called by vfs_read/vfs_write & friends before file_operations .read/.write . Note 2: if file backend uses new-style .read_iter/.write_iter, position is still passed into there as non-pointer kiocb.ki_pos . Currently stream_open.cocci (semantic patch added by 10dce8af3422) ignores files whose file_operations has *_iter methods. Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Kirill Smelkov <kirr@nexedi.com>
2019-04-06fs: stream_open - opener for stream-like files so that read and write can ↵Kirill Smelkov1-0/+18
run simultaneously without deadlock Commit 9c225f2655e3 ("vfs: atomic f_pos accesses as per POSIX") added locking for file.f_pos access and in particular made concurrent read and write not possible - now both those functions take f_pos lock for the whole run, and so if e.g. a read is blocked waiting for data, write will deadlock waiting for that read to complete. This caused regression for stream-like files where previously read and write could run simultaneously, but after that patch could not do so anymore. See e.g. commit 581d21a2d02a ("xenbus: fix deadlock on writes to /proc/xen/xenbus") which fixes such regression for particular case of /proc/xen/xenbus. The patch that added f_pos lock in 2014 did so to guarantee POSIX thread safety for read/write/lseek and added the locking to file descriptors of all regular files. In 2014 that thread-safety problem was not new as it was already discussed earlier in 2006. However even though 2006'th version of Linus's patch was adding f_pos locking "only for files that are marked seekable with FMODE_LSEEK (thus avoiding the stream-like objects like pipes and sockets)", the 2014 version - the one that actually made it into the tree as 9c225f2655e3 - is doing so irregardless of whether a file is seekable or not. See https://lore.kernel.org/lkml/53022DB1.4070805@gmail.com/ https://lwn.net/Articles/180387 https://lwn.net/Articles/180396 for historic context. The reason that it did so is, probably, that there are many files that are marked non-seekable, but e.g. their read implementation actually depends on knowing current position to correctly handle the read. Some examples: kernel/power/user.c snapshot_read fs/debugfs/file.c u32_array_read fs/fuse/control.c fuse_conn_waiting_read + ... drivers/hwmon/asus_atk0110.c atk_debugfs_ggrp_read arch/s390/hypfs/inode.c hypfs_read_iter ... Despite that, many nonseekable_open users implement read and write with pure stream semantics - they don't depend on passed ppos at all. And for those cases where read could wait for something inside, it creates a situation similar to xenbus - the write could be never made to go until read is done, and read is waiting for some, potentially external, event, for potentially unbounded time -> deadlock. Besides xenbus, there are 14 such places in the kernel that I've found with semantic patch (see below): drivers/xen/evtchn.c:667:8-24: ERROR: evtchn_fops: .read() can deadlock .write() drivers/isdn/capi/capi.c:963:8-24: ERROR: capi_fops: .read() can deadlock .write() drivers/input/evdev.c:527:1-17: ERROR: evdev_fops: .read() can deadlock .write() drivers/char/pcmcia/cm4000_cs.c:1685:7-23: ERROR: cm4000_fops: .read() can deadlock .write() net/rfkill/core.c:1146:8-24: ERROR: rfkill_fops: .read() can deadlock .write() drivers/s390/char/fs3270.c:488:1-17: ERROR: fs3270_fops: .read() can deadlock .write() drivers/usb/misc/ldusb.c:310:1-17: ERROR: ld_usb_fops: .read() can deadlock .write() drivers/hid/uhid.c:635:1-17: ERROR: uhid_fops: .read() can deadlock .write() net/batman-adv/icmp_socket.c:80:1-17: ERROR: batadv_fops: .read() can deadlock .write() drivers/media/rc/lirc_dev.c:198:1-17: ERROR: lirc_fops: .read() can deadlock .write() drivers/leds/uleds.c:77:1-17: ERROR: uleds_fops: .read() can deadlock .write() drivers/input/misc/uinput.c:400:1-17: ERROR: uinput_fops: .read() can deadlock .write() drivers/infiniband/core/user_mad.c:985:7-23: ERROR: umad_fops: .read() can deadlock .write() drivers/gnss/core.c:45:1-17: ERROR: gnss_fops: .read() can deadlock .write() In addition to the cases above another regression caused by f_pos locking is that now FUSE filesystems that implement open with FOPEN_NONSEEKABLE flag, can no longer implement bidirectional stream-like files - for the same reason as above e.g. read can deadlock write locking on file.f_pos in the kernel. FUSE's FOPEN_NONSEEKABLE was added in 2008 in a7c1b990f715 ("fuse: implement nonseekable open") to support OSSPD. OSSPD implements /dev/dsp in userspace with FOPEN_NONSEEKABLE flag, with corresponding read and write routines not depending on current position at all, and with both read and write being potentially blocking operations: See https://github.com/libfuse/osspd https://lwn.net/Articles/308445 https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1406 https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1438-L1477 https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1479-L1510 Corresponding libfuse example/test also describes FOPEN_NONSEEKABLE as "somewhat pipe-like files ..." with read handler not using offset. However that test implements only read without write and cannot exercise the deadlock scenario: https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L124-L131 https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L146-L163 https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L209-L216 I've actually hit the read vs write deadlock for real while implementing my FUSE filesystem where there is /head/watch file, for which open creates separate bidirectional socket-like stream in between filesystem and its user with both read and write being later performed simultaneously. And there it is semantically not easy to split the stream into two separate read-only and write-only channels: https://lab.nexedi.com/kirr/wendelin.core/blob/f13aa600/wcfs/wcfs.go#L88-169 Let's fix this regression. The plan is: 1. We can't change nonseekable_open to include &~FMODE_ATOMIC_POS - doing so would break many in-kernel nonseekable_open users which actually use ppos in read/write handlers. 2. Add stream_open() to kernel to open stream-like non-seekable file descriptors. Read and write on such file descriptors would never use nor change ppos. And with that property on stream-like files read and write will be running without taking f_pos lock - i.e. read and write could be running simultaneously. 3. With semantic patch search and convert to stream_open all in-kernel nonseekable_open users for which read and write actually do not depend on ppos and where there is no other methods in file_operations which assume @offset access. 4. Add FOPEN_STREAM to fs/fuse/ and open in-kernel file-descriptors via steam_open if that bit is present in filesystem open reply. It was tempting to change fs/fuse/ open handler to use stream_open instead of nonseekable_open on just FOPEN_NONSEEKABLE flags, but grepping through Debian codesearch shows users of FOPEN_NONSEEKABLE, and in particular GVFS which actually uses offset in its read and write handlers https://codesearch.debian.net/search?q=-%3Enonseekable+%3D https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1080 https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1247-1346 https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1399-1481 so if we would do such a change it will break a real user. 5. Add stream_open and FOPEN_STREAM handling to stable kernels starting from v3.14+ (the kernel where 9c225f2655 first appeared). This will allow to patch OSSPD and other FUSE filesystems that provide stream-like files to return FOPEN_STREAM | FOPEN_NONSEEKABLE in their open handler and this way avoid the deadlock on all kernel versions. This should work because fs/fuse/ ignores unknown open flags returned from a filesystem and so passing FOPEN_STREAM to a kernel that is not aware of this flag cannot hurt. In turn the kernel that is not aware of FOPEN_STREAM will be < v3.14 where just FOPEN_NONSEEKABLE is sufficient to implement streams without read vs write deadlock. This patch adds stream_open, converts /proc/xen/xenbus to it and adds semantic patch to automatically locate in-kernel places that are either required to be converted due to read vs write deadlock, or that are just safe to be converted because read and write do not use ppos and there are no other funky methods in file_operations. Regarding semantic patch I've verified each generated change manually - that it is correct to convert - and each other nonseekable_open instance left - that it is either not correct to convert there, or that it is not converted due to current stream_open.cocci limitations. The script also does not convert files that should be valid to convert, but that currently have .llseek = noop_llseek or generic_file_llseek for unknown reason despite file being opened with nonseekable_open (e.g. drivers/input/mousedev.c) Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Yongzhi Pan <panyongzhi@gmail.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Juergen Gross <jgross@suse.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christoph Hellwig <hch@lst.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Julia Lawall <Julia.Lawall@lip6.fr> Cc: Nikolaus Rath <Nikolaus@rath.org> Cc: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Kirill Smelkov <kirr@nexedi.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-29fs/open.c: allow opening only regular files during execve()Tetsuo Handa1-0/+6
syzbot is hitting lockdep warning [1] due to trying to open a fifo during an execve() operation. But we don't need to open non regular files during an execve() operation, for all files which we will need are the executable file itself and the interpreter programs like /bin/sh and ld-linux.so.2 . Since the manpage for execve(2) says that execve() returns EACCES when the file or a script interpreter is not a regular file, and the manpage for uselib(2) says that uselib() can return EACCES, and we use FMODE_EXEC when opening for execve()/uselib(), we can bail out if a non regular file is requested with FMODE_EXEC set. Since this deadlock followed by khungtaskd warnings is trivially reproducible by a local unprivileged user, and syzbot's frequent crash due to this deadlock defers finding other bugs, let's workaround this deadlock until we get a chance to find a better solution. [1] https://syzkaller.appspot.com/bug?id=b5095bfec44ec84213bac54742a82483aad578ce Link: http://lkml.kernel.org/r/1552044017-7890-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Reported-by: syzbot <syzbot+e93a80c1bb7c5c56e522461c149f8bf55eab1b2b@syzkaller.appspotmail.com> Fixes: 8924feff66f35fe2 ("splice: lift pipe_lock out of splice_to_pipe()") Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: Kees Cook <keescook@chromium.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Eric Biggers <ebiggers3@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: <stable@vger.kernel.org> [4.9+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22Merge tag 'ovl-update-4.19' of ↵Linus Torvalds1-21/+23
git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs Pull overlayfs updates from Miklos Szeredi: "This contains two new features: - Stack file operations: this allows removal of several hacks from the VFS, proper interaction of read-only open files with copy-up, possibility to implement fs modifying ioctls properly, and others. - Metadata only copy-up: when file is on lower layer and only metadata is modified (except size) then only copy up the metadata and continue to use the data from the lower file" * tag 'ovl-update-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (66 commits) ovl: Enable metadata only feature ovl: Do not do metacopy only for ioctl modifying file attr ovl: Do not do metadata only copy-up for truncate operation ovl: add helper to force data copy-up ovl: Check redirect on index as well ovl: Set redirect on upper inode when it is linked ovl: Set redirect on metacopy files upon rename ovl: Do not set dentry type ORIGIN for broken hardlinks ovl: Add an inode flag OVL_CONST_INO ovl: Treat metacopy dentries as type OVL_PATH_MERGE ovl: Check redirects for metacopy files ovl: Move some dir related ovl_lookup_single() code in else block ovl: Do not expose metacopy only dentry from d_real() ovl: Open file with data except for the case of fsync ovl: Add helper ovl_inode_realdata() ovl: Store lower data inode in ovl_inode ovl: Fix ovl_getattr() to get number of blocks from lower ovl: Add helper ovl_dentry_lowerdata() to get lower data dentry ovl: Copy up meta inode data from lowest data inode ovl: Modify ovl_lookup() and friends to lookup metacopy dentry ...
2018-07-18Revert "vfs: do get_write_access() on upper layer of overlayfs"Miklos Szeredi1-13/+2
This reverts commit 4d0c5ba2ff79ef9f5188998b29fd28fcb05f3667. We now get write access on both overlay and underlying layers so this patch is no longer needed for correct operation. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18Revert "vfs: add flags to d_real()"Miklos Szeredi1-1/+1
This reverts commit 495e642939114478a5237a7d91661ba93b76f15a. No user of "flags" argument of d_real() remain. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18Revert "ovl: don't allow writing ioctl on lower layer"Miklos Szeredi1-2/+2
This reverts commit 7c6893e3c9abf6a9676e060a1e35e5caca673d57. Overlayfs no longer relies on the vfs for checking writability of files. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18vfs: don't open realMiklos Szeredi1-6/+1
Let overlayfs do its thing when opening a file. This enables stacking and fixes the corner case when a file is opened for read, modified through a writable open, and data is read from the read-only file. After this patch the read-only open will not return stale data even in this case. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-18vfs: make open_with_fake_path() not contribute to nr_filesMiklos Szeredi1-1/+1
Stacking file operations in overlay will store an extra open file for each overlay file opened. The overhead is just that of "struct file" which is about 256bytes, because overlay already pins an extra dentry and inode when the file is open, which add up to a much larger overhead. For fear of breaking working setups, don't start accounting the extra file. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-12new helper: open_with_fake_path()Al Viro1-0/+18
open a file by given inode, faking ->f_path. Use with shitloads of caution - at the very least you'd damn better make sure that some dentry alias of that inode is pinned down by the path in question. Again, this is no general-purpose interface and I hope it will eventually go away. Right now overlayfs wants something like that, but nothing else should. Any out-of-tree code with bright idea of using this one *will* eventually get hurt, with zero notice and great delight on my part. I refuse to use EXPORT_SYMBOL_GPL(), especially in situations when it's really EXPORT_SYMBOL_DONT_USE_IT(), but don't take that export as "you are welcome to use it". Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12->atomic_open(): return 0 in all success casesAl Viro1-2/+2
FMODE_OPENED can be used to distingusish "successful open" from the "called finish_no_open(), do it yourself" cases. Since finish_no_open() has been adjusted, no changes in the instances were actually needed. The caller has been adjusted. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12getting rid of 'opened' argument of ->atomic_open() - part 1Al Viro1-2/+1
'opened' argument of finish_open() is unused. Kill it. Signed-off-by Al Viro <viro@zeniv.linux.org.uk>
2018-07-12switch all remaining checks for FILE_OPENED to FMODE_OPENEDAl Viro1-7/+2
... and don't bother with setting FILE_OPENED at all. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12now we can fold open_check_o_direct() into do_dentry_open()Al Viro1-12/+5
These checks are better off in do_dentry_open(); the reason we couldn't put them there used to be that callers couldn't tell what kind of cleanup would do_dentry_open() failure call for. Now that we have FMODE_OPENED, cleanup is the same in all cases - it's simply fput(). So let's fold that into do_dentry_open(), as Christoph's patch tried to. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12fold put_filp() into fput()Al Viro1-8/+3
Just check FMODE_OPENED in __fput() and be done with that... Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12introduce FMODE_OPENEDAl Viro1-1/+2
basically, "is that instance set up enough for regular fput(), or do we want put_filp() for that one". NOTE: the only alloc_file() caller that could be followed by put_filp() is in arch/ia64/kernel/perfmon.c, which is (Kconfig-level) broken. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12security_file_open(): lose cred argumentAl Viro1-1/+1
Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12get rid of cred argument of vfs_open() and do_dentry_open()Al Viro1-9/+6
always equal to ->f_cred Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12pass ->f_flags value to alloc_empty_file()Al Viro1-5/+3
... and have it set the f_flags-derived part of ->f_mode. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12pass creds to get_empty_filp(), make sure dentry_open() passes the right credsAl Viro1-1/+1
... and rename get_empty_filp() to alloc_empty_file(). dentry_open() gets creds as argument, but the only thing that sees those is security_file_open() - file->f_cred still ends up with current_cred(). For almost all callers it's the same thing, but there are several broken cases. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-11make sure do_dentry_open() won't return positive as an errorAl Viro1-0/+2
An ->open() instances really, really should not be doing that. There's a lot of places e.g. around atomic_open() that could be confused by that, so let's catch that early. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-11turn filp_clone_open() into inline wrapper for dentry_open()Al Viro1-20/+0
it's exactly the same thing as dentry_open(&file->f_path, file->f_flags, file->f_cred) ... and rename it to file_clone_open(), while we are at it. 'filp' naming convention is bogus; sure, it's "file pointer", but we generally don't do that kind of Hungarian notation. Some of the instances have too many callers to touch, but this one has only two, so let's sanitize it while we can... Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>