CRED: Fix kernel panic upon security_file_alloc() failure.
Tetsuo Handa [Fri, 4 Feb 2011 18:13:24 +0000 (18:13 +0000)]
In get_empty_filp() since 2.6.29, file_free(f) is called with f->f_cred == NULL
when security_file_alloc() returned an error.  As a result, kernel will panic()
due to put_cred(NULL) call within RCU callback.

Fix this bug by assigning f->f_cred before calling security_file_alloc().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/file_table.c

index c3e89ad..eb36b6b 100644 (file)
@@ -125,13 +125,13 @@ struct file *get_empty_filp(void)
                goto fail;
 
        percpu_counter_inc(&nr_files);
+       f->f_cred = get_cred(cred);
        if (security_file_alloc(f))
                goto fail_sec;
 
        INIT_LIST_HEAD(&f->f_u.fu_list);
        atomic_long_set(&f->f_count, 1);
        rwlock_init(&f->f_owner.lock);
-       f->f_cred = get_cred(cred);
        spin_lock_init(&f->f_lock);
        eventpoll_init_file(f);
        /* f->f_version: 0 */