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authorEric Dumazet <edumazet@google.com>2017-02-04 11:16:52 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-18 16:39:26 +0100
commit2d9c2e011fd3f1be4e5643d6ad186faa5e50d4d1 (patch)
tree11e4e29d36c46efe59c2f06050fd8becf8fc8f11 /net
parent22449a01baa59fc7fb2a09df26f55faf967828bc (diff)
ipv4: keep skb->dst around in presence of IP options
[ Upstream commit 34b2cef20f19c87999fff3da4071e66937db9644 ] 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/ip_sockglue.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 9ce202549e7a..bc14c5bb124b 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1192,7 +1192,14 @@ 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,