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From: YueHaibing <yuehaibing@huawei.com>
To: <steffen.klassert@secunet.com>, <herbert@gondor.apana.org.au>,
	<davem@davemloft.net>, <kuba@kernel.org>, <timo.teras@iki.fi>
Cc: <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	YueHaibing <yuehaibing@huawei.com>
Subject: [PATCH] xfrm: policy: Fix doulbe free in xfrm_policy_timer
Date: Wed, 18 Mar 2020 11:48:39 +0800	[thread overview]
Message-ID: <20200318034839.57996-1-yuehaibing@huawei.com> (raw)

After xfrm_add_policy add a policy, its ref is 2, then

                             xfrm_policy_timer
                               read_lock
                               xp->walk.dead is 0
                               ....
                               mod_timer()
xfrm_policy_kill
  policy->walk.dead = 1
  ....
  del_timer(&policy->timer)
    xfrm_pol_put //ref is 1
  xfrm_pol_put  //ref is 0
    xfrm_policy_destroy
      call_rcu
                                 xfrm_pol_hold //ref is 1
                               read_unlock
                               xfrm_pol_put //ref is 0
                                 xfrm_policy_destroy
                                  call_rcu

xfrm_policy_destroy is called twice, which may leads to
double free.

Call Trace:
RIP: 0010:refcount_warn_saturate+0x161/0x210
...
 xfrm_policy_timer+0x522/0x600
 call_timer_fn+0x1b3/0x5e0
 ? __xfrm_decode_session+0x2990/0x2990
 ? msleep+0xb0/0xb0
 ? _raw_spin_unlock_irq+0x24/0x40
 ? __xfrm_decode_session+0x2990/0x2990
 ? __xfrm_decode_session+0x2990/0x2990
 run_timer_softirq+0x5c5/0x10e0

Fix this by add write_lock_bh in xfrm_policy_kill.

Fixes: ea2dea9dacc2 ("xfrm: remove policy lock when accessing policy->walk.dead")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
---
 net/xfrm/xfrm_policy.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index dbda08ec566e..ae0689174bbf 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -434,6 +434,7 @@ EXPORT_SYMBOL(xfrm_policy_destroy);
 
 static void xfrm_policy_kill(struct xfrm_policy *policy)
 {
+	write_lock_bh(&policy->lock);
 	policy->walk.dead = 1;
 
 	atomic_inc(&policy->genid);
@@ -445,6 +446,7 @@ static void xfrm_policy_kill(struct xfrm_policy *policy)
 	if (del_timer(&policy->timer))
 		xfrm_pol_put(policy);
 
+	write_lock_bh(&policy->lock);
 	xfrm_pol_put(policy);
 }
 
-- 
2.17.1



             reply	other threads:[~2020-03-18  3:50 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-18  3:48 YueHaibing [this message]
2020-03-20 12:37 ` [PATCH] xfrm: policy: Fix doulbe free in xfrm_policy_timer Dan Carpenter
2020-03-20 12:37   ` Dan Carpenter
2020-03-23  1:41 ` [PATCH v2] " YueHaibing
2020-03-23  6:29   ` Herbert Xu
2020-03-23  7:04     ` Yuehaibing
2020-03-23  6:53   ` Timo Teras
2020-03-23  7:21     ` Yuehaibing
2020-03-23  7:56       ` Timo Teras
2020-03-23  7:32 ` [PATCH v3] " YueHaibing
2020-03-23  8:00   ` Timo Teras
2020-03-23 21:44   ` Herbert Xu
2020-03-25 12:53   ` Steffen Klassert

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