linux-kernel - [PATCH] ipc: initialize structure memory to zero for shmctl

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Message-ID: <20101007001031.GX14666@outflux.net>
Date:	Wed, 6 Oct 2010 17:10:31 -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>, stable@...nel.org
Subject: [PATCH] ipc: initialize structure memory to zero for shmctl

The old shm interface will leak a few bytes of stack contents. Explicitly
initialize the structure to zero-fill the untouched fields.

Signed-off-by: Kees Cook <kees.cook@...onical.com>
---
 ipc/shm.c |   17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 52ed77e..d2ee426 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -471,16 +471,17 @@ static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_
 		return copy_to_user(buf, in, sizeof(*in));
 	case IPC_OLD:
 	    {
-		struct shmid_ds out;
+		struct shmid_ds out = {
+			.shm_segsz	= in->shm_segsz,
+			.shm_atime	= in->shm_atime,
+			.shm_dtime	= in->shm_dtime,
+			.shm_ctime	= in->shm_ctime,
+			.shm_cpid	= in->shm_cpid,
+			.shm_lpid	= in->shm_lpid,
+			.shm_nattch	= in->shm_nattch,
+		};
 
 		ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
-		out.shm_segsz	= in->shm_segsz;
-		out.shm_atime	= in->shm_atime;
-		out.shm_dtime	= in->shm_dtime;
-		out.shm_ctime	= in->shm_ctime;
-		out.shm_cpid	= in->shm_cpid;
-		out.shm_lpid	= in->shm_lpid;
-		out.shm_nattch	= in->shm_nattch;
 
 		return copy_to_user(buf, &out, sizeof(out));
 	    }
-- 
1.7.1


-- 
Kees Cook
Ubuntu Security Team
--
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