Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
Pre-existing issues: - [High] Unbalanced `pvr_gem_object_get()` in `pvr_vm_gpuva_remap()` causes a permanent memory leak of GEM objects. - [High] Missing `dma_resv` locking during `drm_gpuva_link()` and `drm_gpuva_unlink()` causes data races and list corruption. - [High] Missing `vm_ctx->lock` acquisition in `pvr_vm_map()` causes concurrent execution data races and potential RB tree corruption. -- --- Patch [1]: [PATCH 1/4] drm/imagination: Fix the vm_bo split mappings are linked to --- commit c145cb50bdcd3046dfd6222a4b0282d9524af76c Author: Gyeyoung Baek <[email protected]> drm/imagination: Fix the vm_bo split mappings are linked to A remap does not map anything new. It splits an existing mapping and re-creates the parts the request did not cover, and that mapping is handed to the callback in op->remap.unmap->va, carrying the &drm_gpuvm_bo those parts belong to. > diff --git a/drivers/gpu/drm/imagination/pvr_vm.c > b/drivers/gpu/drm/imagination/pvr_vm.c > index 396d349fb6ce4..608e8c0467dce 100644 > --- a/drivers/gpu/drm/imagination/pvr_vm.c > +++ b/drivers/gpu/drm/imagination/pvr_vm.c > @@ -434,18 +436,18 @@ pvr_vm_gpuva_remap(struct drm_gpuva_op *op, void > *op_ctx) > > if (op->remap.prev) { > pvr_gem_object_get(gem_to_pvr_gem(ctx->prev_va->base.gem.obj)); > - drm_gpuva_link(&ctx->prev_va->base, ctx->gpuvm_bo); > + drm_gpuva_link(&ctx->prev_va->base, vm_bo); [Severity: High] This is a pre-existing issue, but does this code permanently leak GEM objects? During a remap operation, this explicitly calls pvr_gem_object_get() to take references on the backing GEM objects for the new split mappings (prev_va and next_va). However, the teardown paths like pvr_vm_gpuva_unmap() and the unmap phase of pvr_vm_gpuva_remap() just call drm_gpuva_unlink() and kfree() without a corresponding pvr_gem_object_put(). Since the DRM GPUVM framework internally manages GEM object lifetimes through vm_bo structures, are these manual references redundant and never released? [Severity: High] This is another pre-existing issue, but can this cause data races and list corruption? pvr_vm does not use DRM_GPUVM_IMMEDIATE_MODE, so it relies on the GEM object's dma_resv lock to protect gpuva.list operations. When a new mapping overlaps an existing mapping belonging to a different GEM object, the core calls pvr_vm_gpuva_remap() or pvr_vm_gpuva_unmap(). These callbacks then invoke drm_gpuva_link() and drm_gpuva_unlink() on the mappings without holding their GEM object's dma_resv lock. Since pvr_vm_map() only locks the new GEM object being mapped (via pvr_vm_lock_extra()) and doesn't populate the GPUVM's extobj list, does this concurrent lockless modification of gpuva.list result in list corruption? > ctx->prev_va = NULL; > } > > if (op->remap.next) { > pvr_gem_object_get(gem_to_pvr_gem(ctx->next_va->base.gem.obj)); > - drm_gpuva_link(&ctx->next_va->base, ctx->gpuvm_bo); > + drm_gpuva_link(&ctx->next_va->base, vm_bo); > ctx->next_va = NULL; > } > > - drm_gpuva_unlink(op->remap.unmap->va); > - kfree(to_pvr_vm_gpuva(op->remap.unmap->va)); > + drm_gpuva_unlink(unmap_va); > + kfree(to_pvr_vm_gpuva(unmap_va)); > > return 0; > } [Severity: High] This is a pre-existing issue in this file outside of the diff, but does pvr_vm_map() have a data race that could corrupt the GPUVM RB-tree? In pvr_vm_unmap(), the driver acquires vm_ctx->lock before searching the GPUVM's RB-tree via drm_gpuva_find(). However, pvr_vm_map() mutates the RB-tree via pvr_vm_bind_op_exec() invoking drm_gpuvm_sm_map() but doesn't acquire vm_ctx->lock: drivers/gpu/drm/imagination/pvr_vm.c:pvr_vm_map() { ... err = pvr_vm_bind_op_exec(&bind_op); ... } While pvr_vm_map() acquires the VM's dma_resv lock, pvr_vm_unmap() does not hold this lock during its traversal: drivers/gpu/drm/imagination/pvr_vm.c:pvr_vm_unmap() { ... va = drm_gpuva_find(&vm_ctx->gpuvm_mgr, device_addr, size); ... } Since there is no shared lock between the reader and writer of the RB-tree, can a map operation modify the tree concurrently with an unmap operation's traversal? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
