Re: WARNING in ion_buffer_destroy

[Laura Abbott]

On 05/09/2018 11:59 PM, Dmitry Vyukov wrote:
> On Wed, Jan 10, 2018 at 7:14 PM, Laura Abbott <labbott@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > 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