From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
To: Florian Westphal <fw@strlen.de>, netdev@vger.kernel.org
Cc: syzbot+c54f457cad330e57e967@syzkaller.appspotmail.com,
syzkaller-bugs@googlegroups.com, netfilter-devel@vger.kernel.org,
Edward Cree <ecree@solarflare.com>
Subject: Re: [PATCH net-next] inet: do not call sublist_rcv on empty list
Date: Tue, 29 Oct 2019 15:35:17 +0200 [thread overview]
Message-ID: <5747d354-66a5-46aa-2b09-b67de8f8e960@cumulusnetworks.com> (raw)
In-Reply-To: <20191029004404.8563-1-fw@strlen.de>
On 29/10/2019 02:44, Florian Westphal wrote:
> syzbot triggered struct net NULL deref in NF_HOOK_LIST:
> RIP: 0010:NF_HOOK_LIST include/linux/netfilter.h:331 [inline]
> RIP: 0010:ip6_sublist_rcv+0x5c9/0x930 net/ipv6/ip6_input.c:292
> ipv6_list_rcv+0x373/0x4b0 net/ipv6/ip6_input.c:328
> __netif_receive_skb_list_ptype net/core/dev.c:5274 [inline]
>
> Reason:
> void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
> struct net_device *orig_dev)
> [..]
> list_for_each_entry_safe(skb, next, head, list) {
> /* iterates list */
> skb = ip6_rcv_core(skb, dev, net);
> /* ip6_rcv_core drops skb -> NULL is returned */
> if (skb == NULL)
> continue;
> [..]
> }
> /* sublist is empty -> curr_net is NULL */
> ip6_sublist_rcv(&sublist, curr_dev, curr_net);
>
> Before the recent change NF_HOOK_LIST did a list iteration before
> struct net deref, i.e. it was a no-op in the empty list case.
>
> List iteration now happens after *net deref, causing crash.
>
> Follow the same pattern as the ip(v6)_list_rcv loop and add a list_empty
> test for the final sublist dispatch too.
>
> Cc: Edward Cree <ecree@solarflare.com>
> Reported-by: syzbot+c54f457cad330e57e967@syzkaller.appspotmail.com
> Fixes: ca58fbe06c54 ("netfilter: add and use nf_hook_slow_list()")
> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
> net/ipv4/ip_input.c | 3 ++-
> net/ipv6/ip6_input.c | 3 ++-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
Fixed my boot problem as well.
Tested-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
next prev parent reply other threads:[~2019-10-29 13:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-28 22:55 general protection fault in ip6_sublist_rcv syzbot
2019-10-29 0:44 ` [PATCH net-next] inet: do not call sublist_rcv on empty list Florian Westphal
2019-10-29 9:21 ` Leon Romanovsky
2019-10-29 13:35 ` Nikolay Aleksandrov [this message]
2019-10-30 0:55 ` David Miller
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