[PATCH 4.14 006/109] ipv4: fix use-after-free in ip_cmsg_recv_dstaddr()

Greg Kroah-Hartman
2018-10-16T17:18:55Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 64199fc0a46ba211362472f7f942f900af9492fd ]

Caching ip_hdr(skb) before a call to pskb_may_pull() is buggy,
do not do it.

Fixes: 2efd4fca703a ("ip: in cmsg IP(V6)_ORIGDSTADDR call pskb_may_pull")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/ip_sockglue.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -147,7 +147,6 @@ static void ip_cmsg_recv_security(struct
static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
{
struct sockaddr_in sin;
- const struct iphdr *iph = ip_hdr(skb);
__be16 *ports;
int end;

@@ -162,7 +161,7 @@ static void ip_cmsg_recv_dstaddr(struct
ports = (__be16 *)skb_transport_header(skb);

sin.sin_family = AF_INET;
- sin.sin_addr.s_addr = iph->daddr;
+ sin.sin_addr.s_addr = ip_hdr(skb)->daddr;
sin.sin_port = ports[1];
memset(sin.sin_zero, 0, sizeof(sin.sin_zero));