net: socket: add check for negative optlen in compat setsockopt

__sys_setsockopt() already checks for `optlen < 0`. Add an equivalent check
to the compat path for robustness. This has to be `> INT_MAX` instead of
`< 0` because the signedness of `optlen` is different here.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/compat.c b/net/compat.c
index 959d1c5..3d34819 100644 (file)
--- a/net/compat.c
+++ b/net/compat.c
@@ -388,8 +388,12 @@ static int __compat_sys_setsockopt(int fd, int level, int optname,
                                   char __user *optval, unsigned int optlen)
 {
        int err;
-       struct socket *sock = sockfd_lookup(fd, &err);
+       struct socket *sock;
+
+       if (optlen > INT_MAX)
+               return -EINVAL;
 
+       sock = sockfd_lookup(fd, &err);
        if (sock) {
                err = security_socket_setsockopt(sock, level, optname);
                if (err) {