drm/amdgpu: validate CP_GFX_SHADOW chunk size in CS pass1

Add a minimum-length check for the AMDGPU_CHUNK_ID_CP_GFX_SHADOW chunk in
amdgpu_cs_pass1(), matching the gate already present for the IB, FENCE and
BO_HANDLES chunk types.

The CP_GFX_SHADOW case previously shared a bare break with the dependency
and syncobj chunk types, which do not dereference a fixed-size struct. When
userspace submits this chunk with length_dw == 0, vmemdup_array_user() is
called with size 0 and returns ZERO_SIZE_PTR, which passes the IS_ERR()
check. amdgpu_cs_p2_shadow() then dereferences chunk->kdata as a struct
drm_amdgpu_cs_chunk_cp_gfx_shadow (reading shadow->flags), faulting on the
ZERO_SIZE_PTR and causing a NULL-pointer dereference.

This is reachable by an unprivileged process in the render group. Reject
undersized chunks with -EINVAL during pass1 so the bad submission is
rejected before pass2 ever dereferences the data.

Fixes: ac9287055ff1 ("drm/amdgpu: add gfx shadow CS IOCTL support")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7f61b2eef7415eccdb40850aca0de94211948657)
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 115b134b4cd1346e66a8904cc5c4da3fc5fc26dc..c2e6495a28bc582a625d7b5d095ce74f312c6b81 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -247,13 +247,17 @@ static int amdgpu_cs_pass1(struct amdgpu_cs_parser *p,
                                goto free_partial_kdata;
                        break;
 
+               case AMDGPU_CHUNK_ID_CP_GFX_SHADOW:
+                       if (size < sizeof(struct drm_amdgpu_cs_chunk_cp_gfx_shadow))
+                               goto free_partial_kdata;
+                       break;
+
                case AMDGPU_CHUNK_ID_DEPENDENCIES:
                case AMDGPU_CHUNK_ID_SYNCOBJ_IN:
                case AMDGPU_CHUNK_ID_SYNCOBJ_OUT:
                case AMDGPU_CHUNK_ID_SCHEDULED_DEPENDENCIES:
                case AMDGPU_CHUNK_ID_SYNCOBJ_TIMELINE_WAIT:
                case AMDGPU_CHUNK_ID_SYNCOBJ_TIMELINE_SIGNAL:
-               case AMDGPU_CHUNK_ID_CP_GFX_SHADOW:
                        break;
 
                default: