netfilter: don't track fragmented packets

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Andrey reports syzkaller splat caused by

NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb)));

in ipv4 nat.  But this assertion (and the comment) are wrong, this function
does see fragments when IP_NODEFRAG setsockopt is used.

As conntrack doesn't track packets without complete l4 header, only the
first fragment is tracked.

Because applying nat to first packet but not the rest makes no sense this
also turns off tracking of all fragments.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

...

This commit is contained in:

Florian Westphal 2017-03-03 21:44:00 +01:00 • committed by Pablo Neira Ayuso

parent 8d70eeb84a

commit 7b4fdf77a4

2 changed files with 4 additions and 5 deletions

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4

net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c

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5

net/ipv4/netfilter/nf_nat_l3proto_ipv4.c

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