The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 488751a0ef9b5ce572c47301ce62d54fc6b5a74d Mon Sep 17 00:00:00 2001

From: Chris Wilson chris@chris-wilson.co.uk Date: Mon, 18 Jan 2021 09:53:32 +0000 Subject: [PATCH] drm/i915/gt: Prevent use of engine->wa_ctx after error

On error we unpin and free the wa_ctx.vma, but do not clear any of the derived flags. During lrc_init, we look at the flags and attempt to dereference the wa_ctx.vma if they are set. To protect the error path where we try to limp along without the wa_ctx, make sure we clear those flags!

Reported-by: Matt Roper matthew.d.roper@intel.com Fixes: 604a8f6f1e33 ("drm/i915/lrc: Only enable per-context and per-bb buffers if set") Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Matt Roper matthew.d.roper@intel.com Cc: Tvrtko Ursulin tvrtko.ursulin@intel.com Cc: Mika Kuoppala mika.kuoppala@linux.intel.com Cc: stable@vger.kernel.org # v4.15+ Reviewed-by: Matt Roper matthew.d.roper@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20210108204026.20682-1-chris@c... (cherry-picked from 5b4dc95cf7f573e927fbbd406ebe54225d41b9b2) Signed-off-by: Jani Nikula jani.nikula@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20210118095332.458813-1-chris@...

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 7614a3d24fca..26c7d0a50585 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -3988,6 +3988,9 @@ static int lrc_setup_wa_ctx(struct intel_engine_cs *engine) static void lrc_destroy_wa_ctx(struct intel_engine_cs *engine) { i915_vma_unpin_and_release(&engine->wa_ctx.vma, 0); + + /* Called on error unwind, clear all flags to prevent further use */ + memset(&engine->wa_ctx, 0, sizeof(engine->wa_ctx)); }

typedef u32 *(*wa_bb_func_t)(struct intel_engine_cs *engine, u32 *batch);