net: socket: error on a negative msg_namelen

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@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/socket.c b/net/socket.c
index 879933aaed4c..32df5847efa3 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1985,6 +1985,10 @@ 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;