linux-kernel - [PATCH 2/2] CRED: Fix memory and refcount leaks upon security_prepare

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Date:	Mon, 07 Feb 2011 13:36:16 +0000
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	David Howells <dhowells@...hat.com>
Subject: [PATCH 2/2] CRED: Fix memory and refcount leaks upon
 security_prepare_creds() failure

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

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@...ove.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@...hat.com>
---

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

diff --git a/kernel/cred.c b/kernel/cred.c
index fcf104b..3a9d6dd 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -657,6 +657,8 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 	validate_creds(old);
 
 	*new = *old;
+	atomic_set(&new->usage, 1);
+	set_cred_subscribers(new, 0);
 	get_uid(new->user);
 	get_group_info(new->group_info);
 
@@ -674,8 +676,6 @@ 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);
 	put_cred(old);
 	validate_creds(new);
 	return new;

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