[34-longterm 099/247] CRED: Fix memory and refcount leaks upon security_prepare_creds() failure

From: Paul Gortmaker
Date: Thu Jun 23 2011 - 14:15:52 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 fb2b2a1d37f80cc818fd4487b510f4e11816e5e1 upstream.

In prepare_kernel_cred() since 2.6.29, put_cred(new) is called without
assigning new->usage when security_prepare_creds() returned an error. As a
result, memory for new and refcount for new->{user,group_info,tgcred} are
leaked because put_cred(new) won't call __put_cred() unless old->usage == 1.

Fix these leaks by assigning new->usage (and new->subscribers which was added
in 2.6.32) before calling security_prepare_creds().

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>
kernel/cred.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index 9a85aee..aa66d6f 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -725,6 +725,8 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)

*new = *old;
+ atomic_set(&new->usage, 1);
+ set_cred_subscribers(new, 0);

@@ -742,8 +744,6 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
goto error;

- atomic_set(&new->usage, 1);
- set_cred_subscribers(new, 0);
return new;

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