Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
Pre-existing issues: - [High] Pre-existing NULL pointer dereference in `pvr_fw_object_destroy()` when handling allocation failures. - [High] Unprotected accesses to `free_list->current_pages` and `free_list->ready_pages` in `pvr_free_list_process_grow_req`. - [High] Firmware commands in the FWCCB can be processed out of order due to lock dropping in `pvr_fwccb_process`. -- --- Patch [1]: [PATCH] drm/imagination: Remove duplicated CCB control initialisation --- commit f2cf0d89b43f414e7db3141318ab274dbe8aa132 Author: Alessio Belle <[email protected]> drm/imagination: Remove duplicated CCB control initialisation The same is already done by the ccb_ctrl_init() callback. > diff --git a/drivers/gpu/drm/imagination/pvr_ccb.c > b/drivers/gpu/drm/imagination/pvr_ccb.c > index 4accf18e23418..48672a86ca2f5 100644 > --- a/drivers/gpu/drm/imagination/pvr_ccb.c > +++ b/drivers/gpu/drm/imagination/pvr_ccb.c > @@ -82,11 +82,6 @@ pvr_ccb_init(struct pvr_device *pvr_dev, struct pvr_ccb > *pvr_ccb, > pvr_fw_object_get_fw_addr(pvr_ccb->ctrl_obj, &pvr_ccb->ctrl_fw_addr); > pvr_fw_object_get_fw_addr(pvr_ccb->ccb_obj, &pvr_ccb->ccb_fw_addr); > > - WRITE_ONCE(pvr_ccb->ctrl->write_offset, 0); > - WRITE_ONCE(pvr_ccb->ctrl->read_offset, 0); > - WRITE_ONCE(pvr_ccb->ctrl->wrap_mask, num_cmds - 1); > - WRITE_ONCE(pvr_ccb->ctrl->cmd_size, cmd_size); > - > return 0; > > err_free_ctrl: This isn't a bug introduced by this patch, but I noticed a potential NULL pointer dereference in pvr_fw_object_destroy() when handling allocation failures. If pvr_gem_object_create() fails in pvr_fw_object_create_and_map_common(), fw_obj->gem is explicitly set to NULL before jumping to the error cleanup path: drivers/gpu/drm/imagination/pvr_fw.c:pvr_fw_object_create_and_map_common() { ... fw_obj->gem = pvr_gem_object_create(pvr_dev, size, flags); if (IS_ERR(fw_obj->gem)) { err = PTR_ERR(fw_obj->gem); fw_obj->gem = NULL; goto err_put_object; } ... err_put_object: pvr_fw_object_destroy(fw_obj); return ERR_PTR(err); } The cleanup path then calls pvr_fw_object_destroy(): drivers/gpu/drm/imagination/pvr_fw.c:pvr_fw_object_destroy() { struct pvr_gem_object *pvr_obj = fw_obj->gem; struct drm_gem_object *gem_obj = gem_from_pvr_gem(pvr_obj); struct pvr_device *pvr_dev = to_pvr_device(gem_obj->dev); [Severity: High] Will this unconditionally dereference the NULL gem_obj (derived from the NULL fw_obj->gem) to get the device, causing a kernel panic? This is a pre-existing issue, but there appears to be an unprotected access to the free list page accounting variables in pvr_free_list_process_grow_req(). drivers/gpu/drm/imagination/pvr_free_list.c:pvr_free_list_process_grow_req() { ... /* Since the FW made the request, it has already consumed the ready pages, * update the host struct. */ free_list->current_pages += free_list->ready_pages; free_list->ready_pages = 0; /* If the grow succeeds, update the grow_pages argument. */ if (!pvr_free_list_grow(free_list, free_list->grow_pages)) grow_pages = free_list->grow_pages; /* Now prepare the response and send it back to the FW. */ pvr_fw_object_get_fw_addr(free_list->fw_obj, &resp->freelist_fw_addr); resp->delta_pages = grow_pages; resp->new_pages = free_list->current_pages + free_list->ready_pages; ... } [Severity: High] Since pvr_fwccb_process() can run concurrently (from the IRQ handler and userspace-triggered free list release), can these unprotected modifications and reads of free_list->current_pages and free_list->ready_pages lead to data corruption in the free list page accounting? This isn't a bug introduced by this patch, but I noticed that firmware commands in the FWCCB might be processed out of order because the lock is dropped in pvr_fwccb_process(). drivers/gpu/drm/imagination/pvr_ccb.c:pvr_fwccb_process() { ... while ((read_offset = READ_ONCE(ctrl->read_offset)) != READ_ONCE(ctrl->write_offset)) { struct rogue_fwif_fwccb_cmd cmd = fwccb[read_offset]; WRITE_ONCE(ctrl->read_offset, (read_offset + 1) & READ_ONCE(ctrl->wrap_mask)); /* Drop FWCCB lock while we process command. */ mutex_unlock(&pvr_dev->fwccb.lock); process_fwccb_command(pvr_dev, &cmd); mutex_lock(&pvr_dev->fwccb.lock); } ... } [Severity: High] Since this function can be called both from the IRQ thread and from the userspace-triggered pvr_free_list_release() path, if one thread dequeues a command and drops the lock, could a second thread acquire the lock, dequeue the next command, and process it concurrently, leading to out-of-order execution of firmware events? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/20260810-b4-upstream-remove-duplicate-ccb-control-init-v1-1-4ea79b116...@imgtec.com?part=1
