Commit 4c59406e authored by YueHaibing's avatar YueHaibing Committed by Steffen Klassert

xfrm: policy: Fix doulbe free in xfrm_policy_timer

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 use write_lock_bh in xfrm_policy_kill.

Fixes: ea2dea9d ("xfrm: remove policy lock when accessing policy->walk.dead")
Signed-off-by: default avatarYueHaibing <yuehaibing@huawei.com>
Acked-by: default avatarTimo Teräs <timo.teras@iki.fi>
Acked-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent 2a9de3af
...@@ -434,7 +434,9 @@ EXPORT_SYMBOL(xfrm_policy_destroy); ...@@ -434,7 +434,9 @@ EXPORT_SYMBOL(xfrm_policy_destroy);
static void xfrm_policy_kill(struct xfrm_policy *policy) static void xfrm_policy_kill(struct xfrm_policy *policy)
{ {
write_lock_bh(&policy->lock);
policy->walk.dead = 1; policy->walk.dead = 1;
write_unlock_bh(&policy->lock);
atomic_inc(&policy->genid); atomic_inc(&policy->genid);
......
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