CRED: Fix kernel panic upon security_file_alloc() failure.

commit 78d2978874e4e10e97dfd4fd79db45bdc0748550 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/file_table.c b/fs/file_table.c
index 32d12b78bac8e2c05a80dc53386b355bdc10ef73..d4be17f188b4f91037df9997d9c334945c080f5b 100644 (file)
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -123,13 +123,13 @@ 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 */