Commit bc909d9d authored Aug 24, 2011 by Mathieu Desnoyers Committed by David S. Miller Aug 24, 2011

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 c71d8ebe 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@efficios.com>
Signed-off-by: David Goulet <dgoulet@ev0ke.net>
CC: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
CC: Anton Blanchard <anton@samba.org>
CC: David S. Miller <davem@davemloft.net>
CC: stable <stable@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent c6f59d13

net/socket.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -1965,8 +1965,9 @@ static int __sys_sendmsg(struct socket sock, struct msghdr __user msg,
		* 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;
		@@ -1978,7 +1979,8 @@ static int __sys_sendmsg(struct socket sock, struct msghdr __user msg,
		*/
		if (used_address && err >= 0) {
		used_address->name_len = msg_sys->msg_namelen;
		memcpy(&used_address->name, msg->msg_name,
		if (msg_sys->msg_name)
		memcpy(&used_address->name, msg_sys->msg_name,
		used_address->name_len);
		}

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