Re: [Intel-gfx] [PATCH] drm/i915: fix use-after-free in page_flip_completed()

[Daniel Vetter]

On Thu, Jan 26, 2017 at 02:46:20PM +0000, Chris Wilson wrote:
> On Thu, Jan 26, 2017 at 05:32:11PM +0300, Andrey Ryabinin wrote:
> > page_flip_completed() dereferences 'work' variable after executing
> > queue_work(). This is not safe as the 'work' item might be already freed
> > by queued work:
> > 
> >     BUG: KASAN: use-after-free in page_flip_completed+0x3ff/0x490 at addr ffff8803dc010f90
> >     Call Trace:
> >      __asan_report_load8_noabort+0x59/0x80
> >      page_flip_completed+0x3ff/0x490
> >      intel_finish_page_flip_mmio+0xe3/0x130
> >      intel_pipe_handle_vblank+0x2d/0x40
> >      gen8_irq_handler+0x4a7/0xed0
> >      __handle_irq_event_percpu+0xf6/0x860
> >      handle_irq_event_percpu+0x6b/0x160
> >      handle_irq_event+0xc7/0x1b0
> >      handle_edge_irq+0x1f4/0xa50
> >      handle_irq+0x41/0x70
> >      do_IRQ+0x9a/0x200
> >      common_interrupt+0x89/0x89
> > 
> >     Freed:
> >      kfree+0x113/0x4d0
> >      intel_unpin_work_fn+0x29a/0x3b0
> >      process_one_work+0x79e/0x1b70
> >      worker_thread+0x611/0x1460
> >      kthread+0x241/0x3a0
> >      ret_from_fork+0x27/0x40
> > 
> > Move queue_work() after	trace_i915_flip_complete() to fix this.
> > 
> > Fixes: e5510fac98a7 ("drm/i915: add tracepoints for flip requests & completions")
> > Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> 
> That's old, and indeed does seem to be present from that commit and not
> exposed by something later.
> 
> Cc: <stable@xxxxxxxxxxxxxxx> # v2.6.36+
> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

Applied, thanks for patch&review.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch