[PATCH v2] drm/amdgpu: reject mapping info when BO VA is gone

[Yousef Alhouseen <alhouseenyousef@gmail.com>]

AMDGPU_GEM_OP_GET_MAPPING_INFO looks up the GEM object from the file
handle and then locks the object and VM before resolving the BO-VA. The
GEM object reference keeps the BO alive, but it does not keep the
per-file handle open.

If a racing close drops the last handle reference in that window,
amdgpu_gem_object_close() can remove the BO-VA before
amdgpu_vm_bo_find() runs. The ioctl then walks the BO-VA mapping lists
unconditionally.

Return -EINVAL if the BO is no longer associated with this VM.

Suggested-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Yousef Alhouseen <alhouseenyousef@gmail.com>
---
Changes in v2:
- Describe the handle-close race instead of an initially unmapped BO.
- Return -EINVAL instead of -ENOENT.

 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index 212c14d99..6f5b6f4c2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -1087,6 +1087,12 @@ int amdgpu_gem_op_ioctl(struct drm_device *dev, void *data,
 		struct drm_amdgpu_gem_vm_entry *vm_entries;
 		struct amdgpu_bo_va_mapping *mapping;
 		int num_mappings = 0;
+
+		if (!bo_va) {
+			r = -EINVAL;
+			goto out_exec;
+		}
+
 		/*
 		 * num_entries is set as an input to the size of the user-allocated array of
 		 * drm_amdgpu_gem_vm_entry stored at args->value.
-- 
2.54.0