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

From: Paul Gortmaker
Date: Thu Jun 23 2011 - 14:17:37 EST

From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
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;

+ f->f_cred = get_cred(cred);
if (security_file_alloc(f))
goto fail_sec;

atomic_long_set(&f->f_count, 1);
- f->f_cred = get_cred(cred);
/* f->f_version: 0 */

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/