linux-kernel - Re: general protection fault in _vm_normal

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Message-Id: <20180711140449.3702358d7e8898017e34dcfd@linux-foundation.org>
Date:   Wed, 11 Jul 2018 14:04:49 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     syzbot <syzbot+120abb1c3f7bfdc523f7@...kaller.appspotmail.com>
Cc:     jglisse@...hat.com, kirill.shutemov@...ux.intel.com,
        ldufour@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, mhocko@...e.com, minchan@...nel.org,
        ross.zwisler@...ux.intel.com, sfr@...b.auug.org.au,
        syzkaller-bugs@...glegroups.com, ying.huang@...el.com
Subject: Re: general protection fault in _vm_normal_page

On Wed, 11 Jul 2018 09:49:01 -0700 syzbot <syzbot+120abb1c3f7bfdc523f7@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    98be45067040 Add linux-next specific files for 20180711
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=12496ac2400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3f3b3673fec35d01
> dashboard link: https://syzkaller.appspot.com/bug?extid=120abb1c3f7bfdc523f7
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=12a46568400000

Handy.  /dev/ion from drivers/staging/android/ion/ion.c

> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+120abb1c3f7bfdc523f7@...kaller.appspotmail.com
> 
> R10: 0000000004000812 R11: 0000000000000246 R12: 0000000000000005
> R13: 00000000004c0565 R14: 00000000004cffb0 R15: 0000000000000005
> ion_mmap: failure mapping buffer to userspace
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> CPU: 0 PID: 4785 Comm: syz-executor0 Not tainted 4.18.0-rc4-next-20180711+  
> #4
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> RIP: 0010:_vm_normal_page+0x1e5/0x330 mm/memory.c:828

Presumably has a NULL vma->vm_ops.  Probably one of the now-removed
checks in mm-drop-unneeded-vm_ops-checks.patch would have avoided
this.

Something for Kirill to think about ;)