From 21f46f54769c45ac8ca0dbaa977bc1b436ffdee2 Mon Sep 17 00:00:00 2001 From: Srinivasan Shanmugam Date: Tue, 18 Nov 2025 14:28:33 +0530 Subject: [PATCH 5393/5403] drm/amdgpu/ttm: Fix crash when handling MMIO_REMAP in PDE flags MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The MMIO_REMAP BO is a special 4K IO page that does not have a ttm_tt behind it. However, amdgpu_ttm_tt_pde_flags() was treating it like normal TT/doorbell/preempt memory and unconditionally accessed ttm->caching. For the MMIO_REMAP BO, ttm is NULL, so this leads to a NULL pointer dereference when computing PDE flags. Fix this by checking that ttm is non-NULL before reading ttm->caching. This prevents the crash for MMIO_REMAP and also makes the code more defensive if other BOs ever come through without a ttm_tt. Fixes: fb5a52dbe9fe ("drm/amdgpu: Implement TTM handling for MMIO_REMAP placement") Suggested-by: Jesse Zhang Suggested-by: Christian König Cc: Alex Deucher Signed-off-by: Srinivasan Shanmugam Reviewed-by: Jesse Zhang Tested-by: Jesse Zhang Signed-off-by: Alex Deucher (cherry picked from commit 0db94da5a0a1cacda080b9ec8425fcbe4babc141) --- drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index aa9ee5dffa45..9d568c16beb1 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -1372,7 +1372,7 @@ uint64_t amdgpu_ttm_tt_pde_flags(struct ttm_tt *ttm, struct ttm_resource *mem) mem->mem_type == AMDGPU_PL_MMIO_REMAP)) { flags |= AMDGPU_PTE_SYSTEM; - if (ttm->caching == ttm_cached) + if (ttm && ttm->caching == ttm_cached) flags |= AMDGPU_PTE_SNOOPED; } -- 2.54.0