[PATCH 3.11 19/46] net: socket: error on a negative msg_namelen

[Luis Henriques]

3.11.10.8 -stable review patch.  If anyone has any objections, please let me know.

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

From: Matthew Leach <matthew.leach at arm.com>

commit dbb490b96584d4e958533fb637f08b557f505657 upstream.

When copying in a struct msghdr from the user, if the user has set the
msg_namelen parameter to a negative value it gets clamped to a valid
size due to a comparison between signed and unsigned values.

Ensure the syscall errors when the user passes in a negative value.

Signed-off-by: Matthew Leach <matthew.leach at arm.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/socket.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/socket.c b/net/socket.c
index 03d5324..6bfb9e4 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1981,6 +1981,10 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
 {
 	if (copy_from_user(kmsg, umsg, sizeof(struct msghdr)))
 		return -EFAULT;
+
+	if (kmsg->msg_namelen < 0)
+		return -EINVAL;
+
 	if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
 		kmsg->msg_namelen = sizeof(struct sockaddr_storage);
 	return 0;
-- 
1.9.1