linux-kernel - Re: mm: another VM_BUG_ON

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Message-ID: <20160128105136.GD2396@node.shutemov.name>
Date:	Thu, 28 Jan 2016 12:51:36 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Vlastimil Babka <vbabka@...e.cz>,
	Doug Gilbert <dgilbert@...erlog.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Shiraz Hashim <shashim@...eaurora.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Hugh Dickins <hughd@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: mm: another VM_BUG_ON_PAGE(PageTail(page))

On Thu, Jan 28, 2016 at 11:27:11AM +0100, Dmitry Vyukov wrote:
> Hello,
> 
> The following program triggers VM_BUG_ON_PAGE(PageTail(page)):
> 
> // autogenerated by syzkaller (http://github.com/google/syzkaller)
> #include <fcntl.h>
> #include <numaif.h>
> #include <sys/mman.h>
> #include <unistd.h>
> 
> int main()
> {
>   int fd;
> 
>   mmap((void*)0x20000000, 4096, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
>   fd = open("/dev/sg1", O_RDONLY|O_SYNC|0x100000);
>   mmap((void*)0x20001000, 0x4000, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED, fd, 0);
>   mbind((void*)0x20000000, 0x4000, 0x8002, (void*)0x20002ff8, 3660,
> MPOL_MF_STRICT|MPOL_MF_MOVE);
>   return 0;
> }

I don't have sg1 in my VM. I changed it to sg0 and it doesn't trigger an
issue: mbind() returns -EINVAL as it supposed to. Hm..

-- 
 Kirill A. Shutemov