Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Kees Cook <> | Subject | [PATCH] exec: Remove __FMODE_EXEC from uselib() | Date | Wed, 24 Jan 2024 14:06:23 -0800 |
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Path-based LSMs will bypass uselib() "open" checks since commit 4759ff71f23e ("exec: Check __FMODE_EXEC instead of in_execve for LSMs"), so don't set __FMODE_EXEC during uselib(). The LSM "open" and eventual "mmap" hooks will be restored. (uselib() never set current->in_execve.)
Other things that checked __FMODE_EXEC:
- fs/fcntl.c is just doing a bitfield sanity check.
- nfs_open_permission_mask() is only checking for the "unreadable exec" case, which is not an issue for uselib(), which sets MAY_READ, unlike execve().
- fsnotify would no longer see uselib() as FS_OPEN_EXEC_PERM, but rather as FS_OPEN_PERM, but this is likely a bug fix, as uselib() isn't an exec: it's more like mmap(), which fsnotify doesn't intercept.
Reported-by: Jann Horn <jannh@google.com> Closes: https://lore.kernel.org/lkml/CAG48ez017tTwxXbxdZ4joVDv5i8FLWEjk=K_z1Vf=pf0v1=cTg@mail.gmail.com/ Fixes: 4759ff71f23e ("exec: Check __FMODE_EXEC instead of in_execve for LSMs") Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Kevin Locke <kevin@kevinlocke.name> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: linux-mm@kvack.org Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> --- fs/exec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/exec.c b/fs/exec.c index d179abb78a1c..af4fbb61cd53 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -128,7 +128,7 @@ SYSCALL_DEFINE1(uselib, const char __user *, library) struct filename *tmp = getname(library); int error = PTR_ERR(tmp); static const struct open_flags uselib_flags = { - .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, + .open_flag = O_LARGEFILE | O_RDONLY, .acc_mode = MAY_READ | MAY_EXEC, .intent = LOOKUP_OPEN, .lookup_flags = LOOKUP_FOLLOW, -- 2.34.1
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