Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider: - [High] drm/qxl: Race in qxl_irq_fini() leaves hardware interrupts unmasked - [High] drm/qxl: UAF of qdev due to cancel_work_sync() called before free_irq() - [High] drm/qxl: UAF of qdev via gc_work due to missing cancel_work_sync() - [High] drm/qxl: double execution of qxl_irq_fini on probe error path causes UAF --
commit b941d125ca70f91e048fd38f98c81dd403aa9b7d Author: Óscar Megía López <[email protected]> Subject: drm/qxl: fix use-after-free in qxl_irq_handler on PCI This patch attempts to fix a use-after-free in qxl_irq_handler by tearing down the IRQ resources during qxl_device_fini(). It adds qxl_irq_fini() to mask the interrupt, cancel the pending monitor configuration work, and free the IRQ. [ ... ] > --- a/drivers/gpu/drm/qxl/qxl_irq.c > +++ b/drivers/gpu/drm/qxl/qxl_irq.c [ ... ] > @@ -105,3 +105,18 @@ int qxl_irq_init(struct qxl_device *qdev) > } > return 0; > } > + > +void qxl_irq_fini(struct qxl_device *qdev) > +{ > + struct drm_device *ddev = &qdev->ddev; > + struct pci_dev *pdev = to_pci_dev(ddev->dev); > + > + if (qdev->ram_header) { > + qdev->ram_header->int_mask = 0; > + outb(0, qdev->io_base + QXL_IO_UPDATE_IRQ); > + } [Severity: High] Can this masking be overwritten by a concurrent interrupt handler? If qxl_irq_handler() executes on another CPU concurrently, it unconditionally writes QXL_INTERRUPT_MASK to int_mask and QXL_IO_UPDATE_IRQ before returning. If that happens after this block executes, the hardware will remain armed even after free_irq() unregisters the handler, which might cause an unhandled IRQ storm. > + > + cancel_work_sync(&qdev->client_monitors_config_work); > + > + free_irq(pdev->irq, ddev); [Severity: High] Is it safe to cancel the work before freeing the IRQ? Because free_irq() hasn't executed yet, a concurrent interrupt could trigger qxl_irq_handler(). The handler might call: schedule_work(&qdev->client_monitors_config_work) If this happens after cancel_work_sync() has already returned, it would leave the work queued after qdev is freed, resulting in a use-after-free. > +} > --- a/drivers/gpu/drm/qxl/qxl_kms.c > +++ b/drivers/gpu/drm/qxl/qxl_kms.c > @@ -310,6 +310,7 @@ void qxl_device_fini(struct qxl_device *qdev) > qxl_surf_evict(qdev); > qxl_vram_evict(qdev); > > + qxl_irq_fini(qdev); [Severity: High] Is there a risk of a page fault here during probe failure? If qxl_pci_probe() fails, the error path manually calls qxl_device_fini(). Then, devres cleanup triggers qxl_drm_release() which executes qxl_device_fini() a second time. The first execution unmaps qdev->ram_header but doesn't set it to NULL. When the second execution calls qxl_irq_fini(), won't it dereference the unmapped qdev->ram_header? [Severity: High] Will qdev->gc_work remain pending after device teardown? Earlier in qxl_device_fini(), flush_work(&qdev->gc_work) is called, followed by qxl_surf_evict() and qxl_vram_evict(). These evictions can push commands to the hardware, resulting in new interrupts. Since qxl_irq_fini() hasn't been called yet, qxl_irq_handler() processes these interrupts and calls qxl_queue_garbage_collect(), which re-schedules gc_work. Since cancel_work_sync(&qdev->gc_work) is never called, couldn't this lead to a use-after-free when the pending work executes later? > qxl_gem_fini(qdev); > qxl_bo_fini(qdev); > qxl_ring_free(qdev->command_ring); -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1
