From: Linus Torvalds torvalds@linux-foundation.org
mainline inclusion from mainline-v6.8-rc2 commit 3eab830189d94f0f80f34cbff609b5bb54002679 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IAZ996 CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Jann Horn points out that uselib() really shouldn't trigger the new FMODE_EXEC logic introduced by commit 4759ff71f23e ("exec: __FMODE_EXEC instead of in_execve for LSMs").
In fact, it shouldn't even have ever triggered the old pre-existing logic for __FMODE_EXEC (like the NFS code that makes executables not need read permissions). Unlike a real execve(), that can work even with files that are purely executable by the user (not readable), uselib() has that MAY_READ requirement becasue it's really just a convenience wrapper around mmap() for legacy shared libraries.
The whole FMODE_EXEC bit was originally introduced by commit b500531e6f5f ("[PATCH] Introduce FMODE_EXEC file flag"), primarily to give ETXTBUSY error returns for distributed filesystems.
It has since grown a few other warts (like that NFS thing), but there really isn't any reason to use it for uselib(), and now that we are trying to use it to replace the horrid 'tsk->in_execve' flag, it's actively wrong.
Of course, as Jann Horn also points out, nobody should be enabling CONFIG_USELIB in the first place in this day and age, but that's a different discussion entirely.
Reported-by: Jann Horn jannh@google.com Fixes: 4759ff71f23e ("exec: __FMODE_EXEC instead of in_execve for LSMs") Cc: Kees Cook keescook@chromium.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Gu Bowen gubowen5@huawei.com --- fs/exec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/exec.c b/fs/exec.c index 54209b0a5eab..a2f6fffcda57 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -132,7 +132,7 @@ 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,