Re: (subset) [PATCH 2/2] drm/imagination: Fix error path in pvr_vm_create_context

[Maxime Ripard]

On Wed, 13 Dec 2023 14:44:31 +, Donald Robson wrote:
> It is possible to double free the vm_ctx->mmu_ctx object in this
> function.
> 
>     630 err_page_table_destroy:
> --> 631 pvr_mmu_context_destroy(vm_ctx->mmu_ctx);
> 
> The pvr_vm_context_put() function does:
> 
> [...]

Applied to drm/drm-misc (drm-misc-next-fixes).

Thanks!
Maxime

Re: [PATCH 2/2] drm/imagination: Fix error path in pvr_vm_create_context

[Dan Carpenter]

Thanks so much.

Reviewed-by: Dan Carpenter 

regards,
dan carpenter

[PATCH 2/2] drm/imagination: Fix error path in pvr_vm_create_context

[Donald Robson]

It is possible to double free the vm_ctx->mmu_ctx object in this
function.

    630 err_page_table_destroy:
--> 631 pvr_mmu_context_destroy(vm_ctx->mmu_ctx);

The pvr_vm_context_put() function does:

    kref_put(&vm_ctx->ref_count, pvr_vm_context_release);

Here the pvr_vm_context_release() will call:

    pvr_mmu_context_destroy(vm_ctx->mmu_ctx);

Refactor to an unwind style.

Reported-by: Dan Carpenter 
Signed-off-by: Donald Robson 
---
 drivers/gpu/drm/imagination/pvr_vm.c | 28 +---
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_vm.c 
b/drivers/gpu/drm/imagination/pvr_vm.c
index 432168aba577..93155eccc50d 100644
--- a/drivers/gpu/drm/imagination/pvr_vm.c
+++ b/drivers/gpu/drm/imagination/pvr_vm.c
@@ -598,23 +598,12 @@ pvr_vm_create_context(struct pvr_device *pvr_dev, bool 
is_userspace_context)
if (!vm_ctx)
return ERR_PTR(-ENOMEM);
 
-   drm_gem_private_object_init(&pvr_dev->base, &vm_ctx->dummy_gem, 0);
-
vm_ctx->pvr_dev = pvr_dev;
-   kref_init(&vm_ctx->ref_count);
-   mutex_init(&vm_ctx->lock);
-
-   drm_gpuvm_init(&vm_ctx->gpuvm_mgr,
-  is_userspace_context ? "PowerVR-user-VM" : 
"PowerVR-FW-VM",
-  0, &pvr_dev->base, &vm_ctx->dummy_gem,
-  0, 1ULL << device_addr_bits, 0, 0, &pvr_vm_gpuva_ops);
 
vm_ctx->mmu_ctx = pvr_mmu_context_create(pvr_dev);
err = PTR_ERR_OR_ZERO(vm_ctx->mmu_ctx);
-   if (err) {
-   vm_ctx->mmu_ctx = NULL;
-   goto err_put_ctx;
-   }
+   if (err)
+   goto err_free;
 
if (is_userspace_context) {
err = pvr_fw_object_create(pvr_dev, sizeof(struct 
rogue_fwif_fwmemcontext),
@@ -625,13 +614,22 @@ pvr_vm_create_context(struct pvr_device *pvr_dev, bool 
is_userspace_context)
goto err_page_table_destroy;
}
 
+   drm_gem_private_object_init(&pvr_dev->base, &vm_ctx->dummy_gem, 0);
+   drm_gpuvm_init(&vm_ctx->gpuvm_mgr,
+  is_userspace_context ? "PowerVR-user-VM" : 
"PowerVR-FW-VM",
+  0, &pvr_dev->base, &vm_ctx->dummy_gem,
+  0, 1ULL << device_addr_bits, 0, 0, &pvr_vm_gpuva_ops);
+
+   mutex_init(&vm_ctx->lock);
+   kref_init(&vm_ctx->ref_count);
+
return vm_ctx;
 
 err_page_table_destroy:
pvr_mmu_context_destroy(vm_ctx->mmu_ctx);
 
-err_put_ctx:
-   pvr_vm_context_put(vm_ctx);
+err_free:
+   kfree(vm_ctx);
 
return ERR_PTR(err);
 }
-- 
2.25.1