From: "Paul E. McKenney" <paulmck@kernel.org>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
kbuild@01.org, kbuild-all@01.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [rcu:dev.2019.09.23a 62/77] kernel/rcu/tree.c:2882 kfree_call_rcu() warn: inconsistent returns 'irqsave:flags'.
Date: Tue, 24 Sep 2019 09:03:48 -0700 [thread overview]
Message-ID: <20190924160348.GF2689@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <CAEXW_YQYDom3AwWR1AUSCw5VvFzc6KrBH0KbuTvhkJ3OoxBfCg@mail.gmail.com>
On Tue, Sep 24, 2019 at 08:15:12AM -0400, Joel Fernandes wrote:
> On Tue, Sep 24, 2019 at 4:05 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >
> > tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2019.09.23a
> > head: 97de53b94582c208ee239178b208b8e8b9472585
> > commit: 39676bb72323718a9e7bab1ba9c4a68319a96f62 [62/77] rcu: Add support for debug_objects debugging for kfree_rcu()
> >
> > If you fix the issue, kindly add following tag
> > Reported-by: kbuild test robot <lkp@intel.com>
> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> > smatch warnings:
> > kernel/rcu/tree.c:2882 kfree_call_rcu() warn: inconsistent returns 'irqsave:flags'.
> > Locked on: line 2867
> > Unlocked on: line 2882
> >
> > git remote add rcu https://kernel.googlesource.com/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
> > git remote update rcu
> > git checkout 39676bb72323718a9e7bab1ba9c4a68319a96f62
> > vim +2882 kernel/rcu/tree.c
> >
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2850) void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2851) {
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2852) unsigned long flags;
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2853) struct kfree_rcu_cpu *krcp;
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2854)
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2855) head->func = func;
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2856)
> > 87970ccf5a9125 Paul E. McKenney 2019-09-19 2857 local_irq_save(flags); // For safely calling this_cpu_ptr().
> > ^^^^^^^^^^^^^^^^^^^^^
> > IRQs disabled.
> >
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2858) krcp = this_cpu_ptr(&krc);
> > ff8db005e371cb Paul E. McKenney 2019-09-19 2859 if (krcp->initialized)
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2860) spin_lock(&krcp->lock);
> > 5f5046cc15d514 Joel Fernandes (Google 2019-08-05 2861)
> > 87970ccf5a9125 Paul E. McKenney 2019-09-19 2862 // Queue the object but don't yet schedule the batch.
> > 39676bb7232371 Joel Fernandes (Google 2019-09-22 2863) if (debug_rcu_head_queue(head)) {
> > 39676bb7232371 Joel Fernandes (Google 2019-09-22 2864) // Probable double kfree_rcu(), just leak.
> > 39676bb7232371 Joel Fernandes (Google 2019-09-22 2865) WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
> > 39676bb7232371 Joel Fernandes (Google 2019-09-22 2866) __func__, head);
> > 39676bb7232371 Joel Fernandes (Google 2019-09-22 2867) return;
> >
> > Need to re-enable before returning.
>
> Right. At this point the system has a bug anyway since it is a
> double-free. But yes, no reason to introduce more bugs. Will fix.
> Thank you, Dan!
What Joel said!
As long as I am doing several other reports anyway...
How does the to-be-squashed patch below look?
Thanx, Paul
------------------------------------------------------------------------
commit 39af4c08038a8a6a7b1c9804fdd2c1921d583222
Author: Paul E. McKenney <paulmck@kernel.org>
Date: Tue Sep 24 09:02:00 2019 -0700
squash! rcu: Add support for debug_objects debugging for kfree_rcu()
[ paulmck: Fix IRQ per kbuild test robot <lkp@intel.com> feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 921daa7..edb7539 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2870,7 +2870,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
// Probable double kfree_rcu(), just leak.
WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
__func__, head);
- return;
+ goto unlock_return;
}
head->func = func;
head->next = krcp->head;
@@ -2883,6 +2883,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
}
+unlock_return:
if (krcp->initialized)
spin_unlock(&krcp->lock);
local_irq_restore(flags);
next prev parent reply other threads:[~2019-09-24 16:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-24 8:05 [rcu:dev.2019.09.23a 62/77] kernel/rcu/tree.c:2882 kfree_call_rcu() warn: inconsistent returns 'irqsave:flags' Dan Carpenter
2019-09-24 12:15 ` Joel Fernandes
2019-09-24 16:03 ` Paul E. McKenney [this message]
2019-09-26 18:19 ` Joel Fernandes
2019-09-26 19:24 ` Paul E. McKenney
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