Commit 8b9e5259 authored by Srinivasan Shanmugam's avatar Srinivasan Shanmugam Committed by Alex Deucher
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drm/amdgpu: Fix fence put before wait in amdgpu_amdkfd_submit_ib 



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: 9ae55f03 ("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: default avatarSrinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: default avatarChristian König <christian.koenig@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 47089160

drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c

+2 −2
Original line number Diff line number Diff line
@@ -692,9 +692,9 @@ 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);