[116/165] exec: change uselib(2) IS_SREG() failure to EACCES

Commit Message

Andrew Morton Aug. 12, 2020, 1:36 a.m. UTC

From: Kees Cook <[e-mail]>
Subject: exec: change uselib(2) IS_SREG() failure to EACCES

Patch series "Relocate execve() sanity checks", v2.

While looking at the code paths for the proposed O_MAYEXEC flag, I saw
some things that looked like they should be fixed up.

  exec: Change uselib(2) IS_SREG() failure to EACCES
	This just regularizes the return code on uselib(2).

  exec: Move S_ISREG() check earlier
	This moves the S_ISREG() check even earlier than it was already.

  exec: Move path_noexec() check earlier
	This adds the path_noexec() check to the same place as the
	S_ISREG() check.


This patch (of 3):

Change uselib(2)' S_ISREG() error return to EACCES instead of EINVAL so
the behavior matches execve(2), and the seemingly documented value.  The
"not a regular file" failure mode of execve(2) is explicitly
documented[1], but it is not mentioned in uselib(2)[2] which does,
however, say that open(2) and mmap(2) errors may apply.  The documentation
for open(2) does not include a "not a regular file" error[3], but mmap(2)
does[4], and it is EACCES.

[1] http://man7.org/linux/man-pages/man2/execve.2.html#ERRORS
[2] http://man7.org/linux/man-pages/man2/uselib.2.html#ERRORS
[3] http://man7.org/linux/man-pages/man2/open.2.html#ERRORS
[4] http://man7.org/linux/man-pages/man2/mmap.2.html#ERRORS

Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kees Cook <[e-mail]>
Acked-by: Christian Brauner <[e-mail]>
Cc: Aleksa Sarai <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Eric Biggers <[e-mail]>
Cc: Tetsuo Handa <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 fs/exec.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Patch

--- a/fs/exec.c~exec-change-uselib2-is_sreg-failure-to-eacces
+++ a/fs/exec.c
@@ -141,11 +141,10 @@  SYSCALL_DEFINE1(uselib, const char __use
 	if (IS_ERR(file))
 		goto out;
 
-	error = -EINVAL;
+	error = -EACCES;
 	if (!S_ISREG(file_inode(file)->i_mode))
 		goto exit;
 
-	error = -EACCES;
 	if (path_noexec(&file->f_path))
 		goto exit;