linux-kernel - [028/244] sendmmsg/sendmsg: fix unsafe user pointer access

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Message-Id: <20110928220128.185767598@clark.kroah.org>
Date:	Wed, 28 Sep 2011 14:59:52 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	David Goulet <dgoulet@...ke.net>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Anton Blanchard <anton@...ba.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: [028/244] sendmmsg/sendmsg: fix unsafe user pointer access

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

commit bc909d9ddbf7778371e36a651d6e4194b1cc7d4c upstream.

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 <mathieu.desnoyers@...icios.com>
Signed-off-by: David Goulet <dgoulet@...ke.net>
CC: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
CC: Anton Blanchard <anton@...ba.org>
CC: David S. Miller <davem@...emloft.net>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 net/socket.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/net/socket.c
+++ b/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:

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