4.4-stable review patch. If anyone has any objections, please let me know.
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From: Florian Westphal fw@strlen.de
commit 862591bf4f519d1b8d859af720fafeaebdd0162a upstream.
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 Signed-off-by: Steffen Klassert steffen.klassert@secunet.com Cc: Zubin Mithra zsm@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/xfrm/xfrm_policy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -626,7 +626,8 @@ static void xfrm_hash_rebuild(struct wor
/* re-insert all policies by order of creation */ list_for_each_entry_reverse(policy, &net->xfrm.policy_all, walk.all) { - if (xfrm_policy_id2dir(policy->index) >= XFRM_POLICY_MAX) { + if (policy->walk.dead || + xfrm_policy_id2dir(policy->index) >= XFRM_POLICY_MAX) { /* skip socket policies */ continue; }