linux-kernel - Re: mm: NULL ptr deref in unlink_file

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Date:	Mon, 22 Dec 2014 13:05:13 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>,
	"david S. Miller" <davem@...emloft.net>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>, dave@...olabs.net
Subject: Re: mm: NULL ptr deref in unlink_file_vma

On 12/22/2014 01:01 PM, Kirill A. Shutemov wrote:
> On Mon, Dec 22, 2014 at 10:04:02AM -0500, Sasha Levin wrote:
>> > Hi all,
>> > 
>> > While fuzzing with trinity inside a KVM tools guest running the latest -next
>> > kernel, I've stumbled on the following spew:
>> > 
>> > [  432.376425] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
>> > [  432.378876] IP: down_write (./arch/x86/include/asm/rwsem.h:105 ./arch/x86/include/asm/rwsem.h:121 kernel/locking/rwsem.c:71)
> Looks like vma->vm_file->mapping is NULL. Somebody freed ->vm_file from
> under us?
> 
> I suspect Davidlohr's patchset on i_mmap_lock, but I cannot find any code
> path which could lead to the crash.

I've reported a different issue which that patchset: https://lkml.org/lkml/2014/12/9/741

I guess it could be related?


Thanks,
Sasha
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