From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Will Deacon <will.deacon@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: arm64/v4.16-rc1: KASAN: use-after-free Read in finish_task_switch
Date: Fri, 16 Feb 2018 09:11:27 +0100 [thread overview]
Message-ID: <20180216081127.GE25181@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <206116170.22740.1518739362681.JavaMail.zimbra@efficios.com>
Please trim..
On Fri, Feb 16, 2018 at 12:02:42AM +0000, Mathieu Desnoyers wrote:
> > My current theory: do_exit() gets preempted after having set current->mm
> > to NULL, and after having issued mmput(), which brings the mm_count down
> > to 0.
No it doesn't..
remember, the last thread of a process enters with:
mm_count == 1 && mm_users == 1
exit_mm() then does mmgrab():
mm_count == 2 && mm_users == 1
we then do mmput(), which results in:
mm_count == 1 && mm_users == 0
That last mm_count is for ->active_mm, and will be dropped once we
schedule to a next user task.
next prev parent reply other threads:[~2018-02-16 8:11 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-14 12:02 Mark Rutland
2018-02-14 15:07 ` Will Deacon
2018-02-14 16:51 ` Mark Rutland
2018-02-14 18:53 ` Mathieu Desnoyers
2018-02-15 11:49 ` Peter Zijlstra
2018-02-15 13:13 ` Mathieu Desnoyers
2018-02-15 14:22 ` Will Deacon
2018-02-15 15:33 ` Will Deacon
2018-02-15 16:47 ` Peter Zijlstra
2018-02-15 18:21 ` Will Deacon
2018-02-15 22:08 ` Mathieu Desnoyers
2018-02-16 0:02 ` Mathieu Desnoyers
2018-02-16 8:11 ` Peter Zijlstra [this message]
2018-02-16 16:53 ` Mark Rutland
2018-02-16 17:17 ` Mathieu Desnoyers
2018-02-16 18:33 ` Mark Rutland
2018-02-19 11:26 ` Catalin Marinas
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