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Chris Wilson 142c6a6040 drm/i915: Check for rq->hwsp validity after acquiring RCU lock ... commit 45db630e5f upstream. Since we allow removing the timeline map at runtime, there is a risk that rq->hwsp points into a stale page. To control that risk, we hold the RCU read lock while reading *rq->hwsp, but we missed a couple of important barriers. First, the unpinning / removal of the timeline map must be after all RCU readers into that map are complete, i.e. after an rcu barrier (in this case courtesy of call_rcu()). Secondly, we must make sure that the rq->hwsp we are about to dereference under the RCU lock is valid. In this case, we make the rq->hwsp pointer safe during i915_request_retire() and so we know that rq->hwsp may become invalid only after the request has been signaled. Therefore is the request is not yet signaled when we acquire rq->hwsp under the RCU, we know that rq->hwsp will remain valid for the duration of the RCU read lock. This is a very small window that may lead to either considering the request not completed (causing a delay until the request is checked again, any wait for the request is not affected) or dereferencing an invalid pointer. Fixes: 3adac4689f ("drm/i915: Introduce concept of per-timeline (context) HWSP") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: <stable@vger.kernel.org> # v5.1+ Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201218122421.18344-1-chris@chris-wilson.co.uk (cherry picked from commit 9bb36cf660) Signed-off-by: Jani Nikula <jani.nikula@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210118101755.476744-1-chris@chris-wilson.co.uk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2021-01-27 11:54:56 +01:00
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drm	drm/i915: Check for rq->hwsp validity after acquiring RCU lock	2021-01-27 11:54:56 +01:00
host1x	drm next for 5.10-rc1	2020-10-15 10:46:16 -07:00
ipu-v3	gpu: ipu-v3: remove unused functions	2020-10-26 10:42:38 +01:00
trace	gpu/trace: add a gpu total memory usage tracepoint	2020-03-03 17:52:41 -05:00
vga	vgaarb: mark vga_tryget static	2020-08-01 11:28:17 +02:00
Makefile	gpu/trace: add a gpu total memory usage tracepoint	2020-03-03 17:52:41 -05:00