drm/amdgpu: disallow multiple FENCE chunks in one submit

amdgpu_cs_pass1() dispatches on chunk_id once per chunk without
rejecting repeated ids. p->uf_bo is a single-slot field, so a
submission carrying two AMDGPU_CHUNK_ID_FENCE chunks runs
amdgpu_cs_p1_user_fence() twice, and the second run overwrites
p->uf_bo with a freshly referenced BO without dropping the reference
taken by the first.

amdgpu_cs_parser_fini() only unrefs the final p->uf_bo, so every FENCE
chunk but the last leaks a BO reference. The leaked BO outlives handle
close and process exit.

Reject duplicate FENCE chunks the same way commit fec5f8e8c6bc
("drm/amdgpu: disallow multiple BO_HANDLES chunks in one submit") did
for p->bo_list.

Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Assisted-by: Claude:claude-opus-5
Cc: stable@vger.kernel.org
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 665b1fc2a1845206408f9a2c6da67101789edb82)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index f8bf0f6b5097b03bd1285b67a5c7831764b9199b..6798f6decc376225710c4b4939585924938cc7bb 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -248,6 +248,10 @@ static int amdgpu_cs_pass1(struct amdgpu_cs_parser *p,
                        if (size < sizeof(struct drm_amdgpu_cs_chunk_fence))
                                goto free_partial_kdata;
 
+                       /* Only a single user fence is allowed to simplify handling. */
+                       if (p->uf_bo)
+                               goto free_partial_kdata;
+
                        ret = amdgpu_cs_p1_user_fence(p, p->chunks[i].kdata,
                                                      &uf_offset);
                        if (ret)