[Qemu-stable] [PATCH v2] slirp: udp: fix NULL pointer dereference because of uninitialized socket

[Petr Matousek]

When guest sends udp packet with source port and source addr 0,
uninitialized socket is picked up when looking for matching and already
created udp sockets, and later passed to sosendto() where NULL pointer
dereference is hit during so->slirp->vnetwork_mask.s_addr access.

Fix this by checking that the socket is not just a socket stub.

This is CVE-2014-3640.

Signed-off-by: Petr Matousek <address@hidden>
Reported-by: Xavier Mehrenberger <address@hidden>
Reported-by: Stephane Duverger <address@hidden>
---
v1 -> v2
  * change the check so that it's consistent with the rest of the code

 slirp/udp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/slirp/udp.c b/slirp/udp.c
index 8cc6cb6..f77e00f 100644
--- a/slirp/udp.c
+++ b/slirp/udp.c
@@ -152,7 +152,7 @@ udp_input(register struct mbuf *m, int iphlen)
         * Locate pcb for datagram.
         */
        so = slirp->udp_last_so;
-       if (so->so_lport != uh->uh_sport ||
+       if (so == &slirp->udb || so->so_lport != uh->uh_sport ||
            so->so_laddr.s_addr != ip->ip_src.s_addr) {
                struct socket *tmp;
 
-- 
1.9.3