From: Alysa Liu <Alysa.Liu@amd.com>
Date: Thu, 5 Feb 2026 16:21:45 +0000 (-0500)
Subject: drm/amdgpu: Fix use-after-free race in VM acquire
X-Git-Tag: v7.0-rc3~21^2~4^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2c1030f2e84885cc58bffef6af67d5b9d2e7098f;p=thirdparty%2Fkernel%2Flinux.git

drm/amdgpu: Fix use-after-free race in VM acquire

Replace non-atomic vm->process_info assignment with cmpxchg()
to prevent race when parent/child processes sharing a drm_file
both try to acquire the same VM after fork().

Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alysa Liu <Alysa.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit c7c573275ec20db05be769288a3e3bb2250ec618)
Cc: stable@vger.kernel.org
---

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 06c1913d5a3f..29b400cdd6d5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -1439,7 +1439,10 @@ static int init_kfd_vm(struct amdgpu_vm *vm, void **process_info,
 		*process_info = info;
 	}
 
-	vm->process_info = *process_info;
+	if (cmpxchg(&vm->process_info, NULL, *process_info) != NULL) {
+		ret = -EINVAL;
+		goto already_acquired;
+	}
 
 	/* Validate page directory and attach eviction fence */
 	ret = amdgpu_bo_reserve(vm->root.bo, true);
@@ -1479,6 +1482,7 @@ validate_pd_fail:
 	amdgpu_bo_unreserve(vm->root.bo);
 reserve_pd_fail:
 	vm->process_info = NULL;
+already_acquired:
 	if (info) {
 		dma_fence_put(&info->eviction_fence->base);
 		*process_info = NULL;