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 <herb...@gondor.apana.org.au>
> Cc: Timo Teras <timo.te...@iki.fi>
> Cc: Christophe Gouault <christophe.goua...@6wind.com>
> Reported-by: syzbot
<bot+c028095236fcb6f4348811565b75084c754dc...@syzkaller.appspotmail.com>
> Signed-off-by: Florian Westphal <f...@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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