From 10f64c9dfb1cf1f3a1fa4dfca3f0aa4858dec6d4 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Wed, 27 Dec 2017 23:25:45 +0100 Subject: xfrm: skip policies marked as dead while rehashing 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 Cc: Timo Teras Cc: Christophe Gouault Reported-by: syzbot Signed-off-by: Florian Westphal Signed-off-by: Steffen Klassert Cc: Zubin Mithra Signed-off-by: Greg Kroah-Hartman --- net/xfrm/xfrm_policy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net') diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 3c16aee93dfe..f9a13b67df5e 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -626,7 +626,8 @@ static void xfrm_hash_rebuild(struct work_struct *work) /* 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; } -- cgit v1.2.3