posix_acl: handle NULL ACL in posix_acl_equiv_mode

commit 50c6e28 upstream. Various filesystems don't bother checking for a NULL ACL in posix_acl_equiv_mode, and thus can dereference a NULL pointer when it gets passed one. This usually happens from the NFS server, as the ACL tools never pass a NULL ACL, but instead of one representing the mode bits. Instead of adding boilerplat to all filesystems put this check into one place, which will allow us to remove the check from other filesystems as well later on. Signed-off-by: Christoph Hellwig <[email protected]> Reported-by: Ben Greear <[email protected]> Reported-by: Marco Munderloh <[email protected]>, Cc: Chuck Lever <[email protected]> Signed-off-by: Al Viro <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
jiangmouren · Jun 7, 2014 · 54c2a0c · 54c2a0c
1 parent 1304ba7
commit 54c2a0c
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
@@ -246,6 +246,12 @@ posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 	umode_t mode = 0;
 	int not_equiv = 0;
 
+	/*
+	 * A null ACL can always be presented as mode bits.
+	 */
+	if (!acl)
+		return 0;
+
 	FOREACH_ACL_ENTRY(pa, acl, pe) {
 		switch (pa->e_tag) {
 			case ACL_USER_OBJ: