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sendmmsg/sendmsg: fix unsafe user pointer access

PATCH Applied Mathieu Desnoyers 2 participants 4 messages Aug 25, 2011

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Mathieu Desnoyers

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#0 lore raw

PATCH 1/1 sendmmsg/sendmsg: fix unsafe user pointer access

Dereferencing a user pointer directly from kernel-space without going through the copy_from_user family of functions is a bad idea. Two of such usages can be found in the sendmsg code path called from sendmmsg, added by

commit c71d8ebe7a4496fb7231151cb70a6baa0cb56f9a upstream. commit 5b47b8038f183b44d2d8ff1c7d11a5c1be706b34 in the 3.0-stable tree.

Usages are performed through memcmp() and memcpy() directly. Fix those by using the already copied msg_sys structure instead of the __user *msg structure. Note that msg_sys can be set to NULL by verify_compat_iovec() or verify_iovec(), which requires additional NULL pointer checks.

Signed-off-by Mathieu Desnoyers <[email protected]>
Signed-off-by David Goulet <[email protected]>
CC Tetsuo Handa <[email protected]>
CC Anton Blanchard <[email protected]>
CC David S. Miller <[email protected]>
CC stable <[email protected]>
---
 net/socket.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)
net/socket.c +6 -4
Index: linux-2.6-lttng/net/socket.c
===================================================================
@@ -1965,8 +1965,9 @@ static int __sys_sendmsg(struct socket *
 	 * used_address->name_len is initialized to UINT_MAX so that the first
 	 * destination address never matches.
 	 */
-	if (used_address && used_address->name_len == msg_sys->msg_namelen &&
-	    !memcmp(&used_address->name, msg->msg_name,
+	if (used_address && msg_sys->msg_name &&
+	    used_address->name_len == msg_sys->msg_namelen &&
+	    !memcmp(&used_address->name, msg_sys->msg_name,
 		    used_address->name_len)) {
 		err = sock_sendmsg_nosec(sock, msg_sys, total_len);
 		goto out_freectl;

@@ -1978,8 +1979,9 @@ static int __sys_sendmsg(struct socket *
 	 */
 	if (used_address && err >= 0) {
 		used_address->name_len = msg_sys->msg_namelen;
-		memcpy(&used_address->name, msg->msg_name,
-		       used_address->name_len);
+		if (msg_sys->msg_name)
+			memcpy(&used_address->name, msg_sys->msg_name,
+			       used_address->name_len);
 	}
 
 out_freectl:
Signature · 4 lines
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
maintainer Applied
#1 lore raw

From: Mathieu Desnoyers <[email protected]>
Date: Wed, 24 Aug 2011 22:39:40 -0400

Quoted 13 lines

Dereferencing a user pointer directly from kernel-space without going through the copy_from_user family of functions is a bad idea. Two of such usages can be found in the sendmsg code path called from sendmmsg, added by

commit c71d8ebe7a4496fb7231151cb70a6baa0cb56f9a upstream. commit 5b47b8038f183b44d2d8ff1c7d11a5c1be706b34 in the 3.0-stable tree.

Usages are performed through memcmp() and memcpy() directly. Fix those by using the already copied msg_sys structure instead of the __user *msg structure. Note that msg_sys can be set to NULL by verify_compat_iovec() or verify_iovec(), which requires additional NULL pointer checks.

Quoted 6 lines
Signed-off-by Mathieu Desnoyers <[email protected]>
Signed-off-by David Goulet <[email protected]>
CC Tetsuo Handa <[email protected]>
CC Anton Blanchard <[email protected]>
CC David S. Miller <[email protected]>
CC stable <[email protected]>

Applied, thanks.