linux-kernel - [PATCH] ipc: explicitly clear stack memory in user structs

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Date:	Mon, 25 Oct 2010 16:58:04 -0700
From:	Kees Cook <kees.cook@...onical.com>
To:	linux-kernel@...r.kernel.org
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH] ipc: explicitly clear stack memory in user structs

CVE-2010-4072

The old shm interface will leak a few bytes of stack contents. Explicitly
clear structure using memset instead of C99-style initialization in case
there are ever holes in the packing.

Cc: stable <stable@...nel.org>
Signed-off-by: Kees Cook <kees.cook@...onical.com>
---

This was originally sent as http://lkml.org/lkml/2010/10/6/486 but was
never taken into any tree.

---
 ipc/shm.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 52ed77e..f943b1e 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -473,6 +473,7 @@ static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_
 	    {
 		struct shmid_ds out;
 
+		memset(&out, 0, sizeof(out));
 		ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
 		out.shm_segsz	= in->shm_segsz;
 		out.shm_atime	= in->shm_atime;
@@ -524,6 +525,7 @@ static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminf
 	    {
 		struct shminfo out;
 
+		memset(&out, 0, sizeof(out));
 		if(in->shmmax > INT_MAX)
 			out.shmmax = INT_MAX;
 		else
-- 
1.7.1

-- 
Kees Cook
Ubuntu Security Team
--
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