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sendmmsg/sendmsg: fix unsafe user pointer access

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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 c71d8ebe7a 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>
This commit is contained in:
Mathieu Desnoyers 2011-08-24 19:45:03 -07:00 committed by David S. Miller
parent c6f59d13e2
commit bc909d9ddb
1 changed files with 6 additions and 4 deletions
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10
net/socket.c
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@ -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;
@ -1978,8 +1979,9 @@ 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,
used_address->name_len);
if (msg_sys->msg_name)
memcpy(&used_address->name, msg_sys->msg_name,
used_address->name_len);
}
out_freectl: