From: Liping Zhang <liping.zhang@xxxxxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Liping Zhang <liping.zhang@xxxxxxxxxxxxxx>
---
When I found this problem and want to report it, it was a little too late.
I find that this commit was already pushed to the cgit :(
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 bb77a97..5c0db5c 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);
}
--
2.5.5
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