[PATCH 6.12 126/244] drm/amdgpu: Fix fence put before wait in amdgpu_amdkfd_submit_ib

Greg Kroah-Hartman
2026-03-31T16:51:31Z

From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>

[ Upstream commit 7150850146ebfa4ca998f653f264b8df6f7f85be ]

amdgpu_amdkfd_submit_ib() submits a GPU job and gets a fence
from amdgpu_ib_schedule(). This fence is used to wait for job
completion.

Currently, the code drops the fence reference using dma_fence_put()
before calling dma_fence_wait().

If dma_fence_put() releases the last reference, the fence may be
freed before dma_fence_wait() is called. This can lead to a
use-after-free.

Fix this by waiting on the fence first and releasing the reference
only after dma_fence_wait() completes.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c:697 amdgpu_amdkfd_submit_ib() warn: passing freed memory 'f' (line 696)

Fixes: 9ae55f030dc5 ("drm/amdgpu: Follow up change to previous drm scheduler change.")
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 8b9e5259adc385b61a6590a13b82ae0ac2bd3482)
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
index 84e5364d1f67d..a872da6324865 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
@@ -702,9 +702,9 @@ int amdgpu_amdkfd_submit_ib(struct amdgpu_device *adev,
goto err_ib_sched;
}

- /* Drop the initial kref_init count (see drm_sched_main as example) */
- dma_fence_put(f);
ret = dma_fence_wait(f, false);
+ /* Drop the returned fence reference after the wait completes */
+ dma_fence_put(f);

err_ib_sched:
amdgpu_job_free(job);
--
2.53.0