From 707e6835f89419ff1c05e828c2d9939fd95a7ad8 Mon Sep 17 00:00:00 2001 From: Liping Zhang Date: Sat, 23 Jul 2016 22:16:56 +0800 Subject: [PATCH] netfilter: nf_ct_h323: do not re-activate already expired timer Commit 96d1327ac2e3 ("netfilter: h323: Use mod_timer instead of set_expect_timeout") just simplify the source codes if (!del_timer(&exp->timeout)) return 0; add_timer(&exp->timeout); to mod_timer(&exp->timeout, jiffies + info->timeout * HZ); This is not correct, and introduce a race codition: CPU0 CPU1 - timer expire process_rcf expectation_timed_out lock(exp_lock) - find_exp waiting exp_lock... re-activate timer!! waiting exp_lock... unlock(exp_lock) lock(exp_lock) - unlink expect - free(expect) - unlock(exp_lock) So when the timer expires again, we will access the memory that was already freed. Replace mod_timer with mod_timer_pending here to fix this problem. Fixes: 96d1327ac2e3 ("netfilter: h323: Use mod_timer instead of set_expect_timeout") Cc: Gao Feng Signed-off-by: Liping Zhang Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_h323_main.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c index bb77a97961bf..5c0db5c64734 100644 --- a/net/netfilter/nf_conntrack_h323_main.c +++ b/net/netfilter/nf_conntrack_h323_main.c @@ -1473,7 +1473,8 @@ static int process_rcf(struct sk_buff *skb, struct nf_conn *ct, "timeout to %u seconds for", info->timeout); nf_ct_dump_tuple(&exp->tuple); - mod_timer(&exp->timeout, jiffies + info->timeout * HZ); + mod_timer_pending(&exp->timeout, + jiffies + info->timeout * HZ); } spin_unlock_bh(&nf_conntrack_expect_lock); } -- 2.34.1