[34-longterm 097/247] CRED: Fix kernel panic upon security_file_alloc() failure.

Paul Gortmaker
2011-06-23T18:17:32Z

From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.
-------------------

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: Paul Gortmaker <paul.gortmaker@windriver.com>
---
fs/file_table.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index 32d12b7..d4be17f 100644
--- 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 */
--
1.7.4.4