From f56fe3e91787dc29c2a3e7ec8b7bc3b80f65fbbc Mon Sep 17 00:00:00 2001 From: Nirmoy Das Date: Thu, 8 Jun 2023 13:01:03 +0200 Subject: [PATCH] drm/i915: Fix a VMA UAF for multi-gt platform MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Ensure correct handling of closed VMAs on multi-gt platforms to prevent Use-After-Free. Currently, when GT0 goes idle, closed VMAs that are exclusively added to GT0's closed_vma link (gt->closed_vma) and subsequently freed by i915_vma_parked(), which assumes the entire GPU is idle. However, on platforms with multiple GTs, such as MTL, GT1 may remain active while GT0 is idle. This causes GT0 to mistakenly consider the closed VMAs in its closed_vma list as unnecessary, potentially leading to Use-After-Free issues if a job for GT1 attempts to access a freed VMA. Although we do take a wakeref for GT0 but it happens later, after evaluating VMAs. To mitigate this, it is necessary to hold a GT0 wakeref early. v2: Use gt id to detect multi-tile(Andi) Fix the incorrect error path. v3: Add more comment(Andi) Use the new gt var when possible(Andrzej) Cc: Joonas Lahtinen Cc: Rodrigo Vivi Cc: Tvrtko Ursulin Cc: Thomas Hellström Cc: Chris Wilson Cc: Andi Shyti Cc: Andrzej Hajda Cc: Sushma Venkatesh Reddy Signed-off-by: Nirmoy Das Tested-by: Andi Shyti Reviewed-by: Andi Shyti Reviewed-by: Andrzej Hajda Tested-by: Sushma Venkatesh Reddy Link: https://patchwork.freedesktop.org/patch/msgid/20230608110103.777594-1-andi.shyti@linux.intel.com --- .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 21 +++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index 5fb459ea4294..1de9de1e4782 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -2692,6 +2692,7 @@ static int eb_select_engine(struct i915_execbuffer *eb) { struct intel_context *ce, *child; + struct intel_gt *gt; unsigned int idx; int err; @@ -2715,10 +2716,17 @@ eb_select_engine(struct i915_execbuffer *eb) } } eb->num_batches = ce->parallel.number_children + 1; + gt = ce->engine->gt; for_each_child(ce, child) intel_context_get(child); - intel_gt_pm_get(ce->engine->gt); + intel_gt_pm_get(gt); + /* + * Keep GT0 active on MTL so that i915_vma_parked() doesn't + * free VMAs while execbuf ioctl is validating VMAs. + */ + if (gt->info.id) + intel_gt_pm_get(to_gt(gt->i915)); if (!test_bit(CONTEXT_ALLOC_BIT, &ce->flags)) { err = intel_context_alloc_state(ce); @@ -2757,7 +2765,10 @@ eb_select_engine(struct i915_execbuffer *eb) return err; err: - intel_gt_pm_put(ce->engine->gt); + if (gt->info.id) + intel_gt_pm_put(to_gt(gt->i915)); + + intel_gt_pm_put(gt); for_each_child(ce, child) intel_context_put(child); intel_context_put(ce); @@ -2770,6 +2781,12 @@ eb_put_engine(struct i915_execbuffer *eb) struct intel_context *child; i915_vm_put(eb->context->vm); + /* + * This works in conjunction with eb_select_engine() to prevent + * i915_vma_parked() from interfering while execbuf validates vmas. + */ + if (eb->gt->info.id) + intel_gt_pm_put(to_gt(eb->gt->i915)); intel_gt_pm_put(eb->gt); for_each_child(eb->context, child) intel_context_put(child);