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authorEric Dumazet <edumazet@google.com>2017-02-04 11:16:52 -0800
committerBen Hutchings <ben@decadent.org.uk>2017-02-26 20:01:50 +0000
commit631f00df1b2fa51492de8ab93a91a3876b697aeb (patch)
parent3a997b28bbc69f7637ccd62c5a37379dec34f36b (diff)
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> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
1 files changed, 8 insertions, 1 deletions
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index cf377702852d..ecb2b00b6ad3 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1082,7 +1082,14 @@ 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,