[Intel-gfx] [PATCH] drm/i915: Clean the request structure on alloc

[Daniel Vetter]

On Fri, Dec 05, 2014 at 06:02:35PM +0000, John Harrison wrote:
> But yes, the reasoning why it crashes without the zero fill is correct.
> Dodgy context pointers that used to be ignored now get processed. Doing the
> zero fill keeps it all sane.
> 
> On 05/12/2014 17:54, John Harrison wrote:
> >This is already part of the seqno/request patch series and has been right
> >from the start. See email 'drm/i915: Zero fill the request structure'.
> >
> >On 05/12/2014 17:54, Mika Kuoppala wrote:
> >>Otherwise we might end up referencing uninitialized fields.
> >>This is apparent when we try to cleanup the preallocated request
> >>on ring reset, before any request has been submitted to the ring.
> >>The request->ctx is foobar and we end up freeing the foobarness.
> >>
> >>References: https://bugs.freedesktop.org/show_bug.cgi?id=86959
> >>References: https://bugs.freedesktop.org/show_bug.cgi?id=86962
> >>References: https://bugs.freedesktop.org/show_bug.cgi?id=86992
> >>Cc: John Harrison <John.C.Harrison at Intel.com>
> >>Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>

I've added this explanation plus the note about which commit introduced
the regression to John's patch and merged that one.

Thanks for tracking this down.
-Daniel

> >>---
> >>  drivers/gpu/drm/i915/intel_ringbuffer.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>index 79b4ca5..2c6c6f8 100644
> >>--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>@@ -2030,7 +2030,7 @@ intel_ring_alloc_request(struct intel_engine_cs
> >>*ring)
> >>      if (ring->outstanding_lazy_request)
> >>          return 0;
> >>  -    request = kmalloc(sizeof(*request), GFP_KERNEL);
> >>+    request = kzalloc(sizeof(*request), GFP_KERNEL);
> >>      if (request == NULL)
> >>          return -ENOMEM;
> >
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch