Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Fri, 24 Feb 2017 12:10:01 +0000 | Subject | [PATCH 3.16 10/12] ipv4: keep skb->dst around in presence of IP options |
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3.16.41-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
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> --- net/ipv4/ip_sockglue.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1082,7 +1082,14 @@ void ipv4_pktinfo_prepare(const struct s 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,
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