[PATCH 6.12.y 3/3] drm/amdgpu/gfx: fix cleaner shader IB buffer overflow

[Sasha Levin <sashal@kernel.org>]

From: Asad Kamal <asad.kamal@amd.com>

[ Upstream commit 3e864bf2a32a1cbdf1e0f9c5a5a4176e8575f4a3 ]

The cleaner shader sysfs path allocates a 16-dword (64 byte) IB but
incorrectly fills (align_mask + 1) dwords. On GFX rings align_mask is
0xff, so the loop wrote 256 dwords into a 64-byte buffer, causing a
kernel page fault.

The IB only needs to be a minimal NOP shell to schedule the job; the
cleaner shader itself is emitted on the ring via emit_cleaner_shader().
Fill 16 dwords to match the allocation.

v2: Use ib_size_dw variable (Lijo)

Fixes: d361ad5d2fc0 ("drm/amdgpu: Add sysfs interface for running cleaner shader")
Suggested-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit bf21af331ebf72d0935fd70c73192414a422c03a)
CC: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
index bd9ec01101b0..171603c4ee6c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
@@ -1426,12 +1426,13 @@ static int amdgpu_gfx_run_cleaner_shader_job(struct amdgpu_ring *ring)
 	struct amdgpu_device *adev = ring->adev;
 	struct drm_gpu_scheduler *sched = &ring->sched;
 	struct drm_sched_entity entity;
+	unsigned int ib_size_dw = 16;
 	static atomic_t counter;
 	struct dma_fence *f;
 	struct amdgpu_job *job;
 	struct amdgpu_ib *ib;
 	void *owner;
-	int i, r;
+	int r;
 
 	/* Initialize the scheduler entity */
 	r = drm_sched_entity_init(&entity, DRM_SCHED_PRIORITY_NORMAL,
@@ -1449,7 +1450,7 @@ static int amdgpu_gfx_run_cleaner_shader_job(struct amdgpu_ring *ring)
 	owner = (void *)(unsigned long)atomic_inc_return(&counter);
 
 	r = amdgpu_job_alloc_with_ib(ring->adev, &entity, owner,
-				     64, 0, &job,
+				     ib_size_dw * sizeof(uint32_t), 0, &job,
 				     AMDGPU_KERNEL_JOB_ID_CLEANER_SHADER);
 	if (r)
 		goto err;
@@ -1457,9 +1458,8 @@ static int amdgpu_gfx_run_cleaner_shader_job(struct amdgpu_ring *ring)
 	job->enforce_isolation = true;
 
 	ib = &job->ibs[0];
-	for (i = 0; i <= ring->funcs->align_mask; ++i)
-		ib->ptr[i] = ring->funcs->nop;
-	ib->length_dw = ring->funcs->align_mask + 1;
+	memset32(ib->ptr, ring->funcs->nop, ib_size_dw);
+	ib->length_dw = ib_size_dw;
 
 	f = amdgpu_job_submit(job);
 
-- 
2.53.0