| From 34b2cef20f19c87999fff3da4071e66937db9644 Mon Sep 17 00:00:00 2001 |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Sat, 4 Feb 2017 11:16:52 -0800 |
| Subject: [PATCH] ipv4: keep skb->dst around in presence of IP options |
| |
| commit 34b2cef20f19c87999fff3da4071e66937db9644 upstream. |
| |
| Andrey Konovalov got crashes in __ip_options_echo() when a NULL skb->dst |
| is accessed. |
| |
| ipv4_pktinfo_prepare() should not drop the dst if (evil) IP options |
| are present. |
| |
| We could refine the test to the presence of ts_needtime or srr, |
| but IP options are not often used, so let's be conservative. |
| |
| Thanks to syzkaller team for finding this bug. |
| |
| Fixes: d826eb14ecef ("ipv4: PKTINFO doesnt need dst reference") |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Reported-by: Andrey Konovalov <andreyknvl@google.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| |
| diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c |
| index 53ae0c6315ad..900011709e3b 100644 |
| --- a/net/ipv4/ip_sockglue.c |
| +++ b/net/ipv4/ip_sockglue.c |
| @@ -1238,7 +1238,14 @@ void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb) |
| pktinfo->ipi_ifindex = 0; |
| pktinfo->ipi_spec_dst.s_addr = 0; |
| } |
| - skb_dst_drop(skb); |
| + /* We need to keep the dst for __ip_options_echo() |
| + * We could restrict the test to opt.ts_needtime || opt.srr, |
| + * but the following is good enough as IP options are not often used. |
| + */ |
| + if (unlikely(IPCB(skb)->opt.optlen)) |
| + skb_dst_force(skb); |
| + else |
| + skb_dst_drop(skb); |
| } |
| |
| int ip_setsockopt(struct sock *sk, int level, |
| -- |
| 2.12.0 |
| |
