Re: [PATCH ipsec] xfrm: skip policies marked as dead while rehashing

[syzbot <syzbot+@syzkaller.appspotmail.com>]

> On Sun, Dec 31, 2017 at 08:50:17AM +0100, Steffen Klassert wrote:
>> On Wed, Dec 27, 2017 at 11:25:45PM +0100, Florian Westphal wrote:
>> > syzkaller triggered following KASAN splat:
>> >
>> > BUG: KASAN: slab-out-of-bounds in xfrm_hash_rebuild+0xdbe/0xf00  
>> net/xfrm/xfrm_policy.c:618
>> > read of size 2 at addr ffff8801c8e92fe4 by task kworker/1:1/23 [..]
>> > Workqueue: events xfrm_hash_rebuild [..]
>> >  __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:428
>> >  xfrm_hash_rebuild+0xdbe/0xf00 net/xfrm/xfrm_policy.c:618
>> >  process_one_work+0xbbf/0x1b10 kernel/workqueue.c:2112
>> >  worker_thread+0x223/0x1990 kernel/workqueue.c:2246 [..]
>> >
>> > The reproducer triggers:
>> > 1016                 if (error) {
>> > 1017                         list_move_tail(&walk->walk.all, &x->all);
>> > 1018                         goto out;
>> > 1019                 }
>> >
>> > in xfrm_policy_walk() via pfkey (it sets tiny rcv space, dump
>> > callback returns -ENOBUFS).
>> >
>> > In this case, *walk is located the pfkey socket struct, so this socket
>> > becomes visible in the global policy list.
>> >
>> > It looks like this is intentional -- phony walker has walk.dead set to  
>> 1
>> > and all other places skip such "policies".
>> >
>> > Ccing original authors of the two commits that seem to expose this
>> > issue (first patch missed ->dead check, second patch adds pfkey
>> > sockets to policies dumper list).
>> >
>> > Fixes: 880a6fab8f6ba5b ("xfrm: configure policy hash table thresholds  
>> by netlink")
>> > Fixes: 12a169e7d8f4b1c ("ipsec: Put dumpers on the dump list")
>> > Cc: Herbert Xu <herbert@gondor.apana.org.au>
>> > Cc: Timo Teras <timo.teras@iki.fi>
>> > Cc: Christophe Gouault <christophe.gouault@6wind.com>
>> > Reported-by: syzbot  
>> <bot+c028095236fcb6f4348811565b75084c754dc729@syzkaller.appspotmail.com>
>> > Signed-off-by: Florian Westphal <fw@strlen.de>

>> Applied, thanks a lot!


> This crash seems to have stopped occurring, thanks Florian!  Let's tell  
> syzbot
> so that it can start reporting any crashes in this same place again:

> #syz fix: xfrm: skip policies marked as dead while rehashing

Can't find the corresponding bug.


> - Eric

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