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Subject: Re: WARNING in ion_buffer_destroy
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     syzbot <syzbot+cd8bcd40cb049efa2770@syzkaller.appspotmail.com>,
        =?UTF-8?Q?Arve_Hj=c3=b8nnev=c3=a5g?= <arve@android.com>,
        "open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Martijn Coenen <maco@android.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Todd Kjos <tkjos@android.com>
References: <001a1144928eca24f605625fd8f9@google.com>
 <ee1d01fc-a6a4-9480-9755-b6f25304d08b@redhat.com>
 <CACT4Y+b2Q86dQxsd9_9casAsE9jE8ef87E9WEdKFCYxLkT0Z8A@mail.gmail.com>
From:   Laura Abbott <labbott@redhat.com>
Message-ID: <70de9c10-d7ce-a95b-1bf1-724f9dacaa8c@redhat.com>
Date:   Mon, 14 May 2018 13:37:00 -0700
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On 05/09/2018 11:59 PM, Dmitry Vyukov wrote:
> On Wed, Jan 10, 2018 at 7:14 PM, Laura Abbott <labbott@redhat.com> wrote:
>> On 01/09/2018 02:58 PM, syzbot wrote:
>>>
>>> Hello,
>>>
>>> syzkaller hit the following crash on
>>> 06d41862286aa7bc634a1dd9e6e7e96f925ef30a
>>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
>>> compiler: gcc (GCC) 7.1.1 20170620
>>> .config is attached
>>> Raw console output is attached.
>>> C reproducer is attached
>>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>>> for information about syzkaller reproducers
>>>
>>>
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by: syzbot+cd8bcd40cb049efa2770@syzkaller.appspotmail.com
>>> It will help syzbot understand when the bug is fixed. See footer for
>>> details.
>>> If you forward the report, please keep this part and the footer.
>>>
>>> audit: type=1400 audit(1515538424.230:7): avc:  denied  { map } for
>>> pid=3499 comm="syzkaller239906" path="/root/syzkaller239906633" dev="sda1"
>>> ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
>>> tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
>>> WARNING: CPU: 0 PID: 1467 at drivers/staging/android/ion/ion.c:122
>>> ion_buffer_destroy+0xd4/0x190 drivers/staging/android/ion/ion.c:122
>>> Kernel panic - not syncing: panic_on_warn set ...
>>>
>>> CPU: 0 PID: 1467 Comm: ion_system_heap Not tainted
>>> 4.15.0-rc7-next-20180109+ #92
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>> Google 01/01/2011
>>> Call Trace:
>>>    __dump_stack lib/dump_stack.c:17 [inline]
>>>    dump_stack+0x194/0x257 lib/dump_stack.c:53
>>>    panic+0x1e4/0x41c kernel/panic.c:183
>>>    __warn+0x1dc/0x200 kernel/panic.c:547
>>>    report_bug+0x211/0x2d0 lib/bug.c:184
>>>    fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
>>>    fixup_bug arch/x86/kernel/traps.c:247 [inline]
>>>    do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
>>>    do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
>>>    invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1079
>>> RIP: 0010:ion_buffer_destroy+0xd4/0x190
>>> drivers/staging/android/ion/ion.c:122
>>> RSP: 0018:ffff8801d3a9fd28 EFLAGS: 00010293
>>> RAX: ffff8801d39ee700 RBX: ffff8801c00e57c0 RCX: ffffffff8415d2a4
>>> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801d5ada5b8
>>> RBP: ffff8801d3a9fd50 R08: 0000000000000000 R09: 1ffff1003a753f8a
>>> R10: ffff8801d3a9fc18 R11: 0000000000000000 R12: ffffffff86e4c980
>>> R13: ffff8801d5ada580 R14: ffff8801c00e57e0 R15: 0000000000000001
>>>    ion_heap_deferred_free+0x290/0x650
>>> drivers/staging/android/ion/ion_heap.c:236
>>>    kthread+0x33c/0x400 kernel/kthread.c:238
>>>    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
>>> Dumping ftrace buffer:
>>>      (ftrace buffer empty)
>>> Kernel Offset: disabled
>>> Rebooting in 86400 seconds..
>>
>>
>> This is catching that a buffer was freed with an existing kernel
>> map still present. The problem is this can easily be triggered from
>> userspace by calling DMA_BUF_SYNC_START without calling
>> DMA_BUF_SYNC_END. It's clearly not appropriate for userspace to
>> be able to trigger a warning so I'll see about switching this to
>> a pr_warn_once.
> 
> Hi Laura,
> 
> Any updates on this?
> 

I thought I had sent a fix for this but I guess not. I'll see about
getting one out.

Thanks,
Laura