net: validate the range we feed to iov_iter_init() in sys_sendto/sys_recvfrom

Cc: stable@vger.kernel.org # v3.19
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/socket.c

@@ -1702,6 +1702,8 @@ SYSCALL_DEFINE6(sendto, int, fd, void __user *, buff, size_t, len,
 
 	if (len > INT_MAX)
 		len = INT_MAX;
+	if (unlikely(!access_ok(VERIFY_READ, buff, len)))
+		return -EFAULT;
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (!sock)
 		goto out;
@@ -1760,6 +1762,8 @@ SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, size_t, size,
 
 	if (size > INT_MAX)
 		size = INT_MAX;
+	if (unlikely(!access_ok(VERIFY_WRITE, ubuf, size)))
+		return -EFAULT;
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (!sock)
 		goto out;