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 <fgao@ikuai8.com>
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c
index bb77a97..5c0db5c 100644
--- a/net/netfilter/nf_conntrack_h323_main.c
+++ b/net/netfilter/nf_conntrack_h323_main.c
@@ -1473,7 +1473,8 @@
"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);
}