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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 10 May 2018 08:59:09 +0200
Message-ID: <CACT4Y+b2Q86dQxsd9_9casAsE9jE8ef87E9WEdKFCYxLkT0Z8A@mail.gmail.com>
Subject: Re: WARNING in ion_buffer_destroy
To:     Laura Abbott <labbott@redhat.com>
Cc:     syzbot <syzbot+cd8bcd40cb049efa2770@syzkaller.appspotmail.com>,
        =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <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>
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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?