ipv4: Fix crash in dst_release when udp_sendmsg route lookup fails.

As reported by Eric:

[11483.697233] IP: [<c12b0638>] dst_release+0x18/0x60
 ...
[11483.697741] Call Trace:
[11483.697764]  [<c12fc9d2>] udp_sendmsg+0x282/0x6e0
[11483.697790]  [<c12a1c01>] ? memcpy_toiovec+0x51/0x70
[11483.697818]  [<c12dbd90>] ? ip_generic_getfrag+0x0/0xb0

The pointer passed to dst_release() is -EINVAL, that's because
we leave an error pointer in the local variable "rt" by accident.

NULL it out to fix the bug.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 95e0c2c194a1d42e382b4e89a5fdbb653e2ab928..c9a73e5b26a39289169d3018139c94fd1d88648b 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -925,6 +925,7 @@ int udp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                rt = ip_route_output_flow(net, &fl, sk);
                if (IS_ERR(rt)) {
                        err = PTR_ERR(rt);
+                       rt = NULL;
                        if (err == -ENETUNREACH)
                                IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
                        goto out;