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authorKees Cook <keescook@chromium.org>2017-07-19 01:25:22 +0300
committerKees Cook <keescook@chromium.org>2017-08-01 22:03:05 +0300
commitc425e189ffd7720c881fe9ccd7143cea577f6d03 (patch)
treef5d3154054c9235e033e45afef91bd647e6a8585 /include/linux/binfmts.h
parenta9208e42ba99bfe63bdf5f76aaf0193ad3805f02 (diff)
downloadlinux-c425e189ffd7720c881fe9ccd7143cea577f6d03.tar.xz
binfmt: Introduce secureexec flag
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>
Diffstat (limited to 'include/linux/binfmts.h')
-rw-r--r--include/linux/binfmts.h8
1 files changed, 7 insertions, 1 deletions
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 9023e1d2d5cd..16838ba7ee75 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -31,9 +31,15 @@ struct linux_binprm {
* binfmt_script/misc).
*/
called_set_creds:1,
- cap_effective:1;/* true if has elevated effective capabilities,
+ cap_effective:1,/* true if has elevated effective capabilities,
* false if not; except for init which inherits
* its parent's caps anyway */
+ /*
+ * Set by bprm_set_creds hook to indicate a privilege-gaining
+ * exec has happened. Used to sanitize execution environment
+ * and to set AT_SECURE auxv for glibc.
+ */
+ secureexec:1;
#ifdef __alpha__
unsigned int taso:1;
#endif