On driver unload any pending descriptors are flushed at the time the interrupt is freed: idxd_dmaengine_drv_remove() -> drv_disable_wq() -> idxd_wq_free_irq() -> idxd_flush_pending_descs().
If there are any descriptors present that need to be flushed this flow triggers a "not present" page fault as below:
BUG: unable to handle page fault for address: ff391c97c70c9040 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page
The address that triggers the fault is the address of the descriptor that was freed moments earlier via: drv_disable_wq()->idxd_wq_free_resources()
Fix the use after free by freeing the descriptors after any possible usage. This is done after idxd_wq_reset() to ensure that the memory remains accessible during possible completion writes by the device.
Fixes: 63c14ae6c161 ("dmaengine: idxd: refactor wq driver enable/disable operations") Suggested-by: Dave Jiang dave.jiang@intel.com Signed-off-by: Reinette Chatre reinette.chatre@intel.com Reviewed-by: Dave Jiang dave.jiang@intel.com Reviewed-by: Fenghua Yu fenghua.yu@intel.com Cc: stable@vger.kernel.org --- Changes since V1: - Add Dave and Fenghua's Reviewed-by tags. - cc stable team (Fenghua).
drivers/dma/idxd/device.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c index fcd03d29a941..b4d7bb923a40 100644 --- a/drivers/dma/idxd/device.c +++ b/drivers/dma/idxd/device.c @@ -1408,11 +1408,11 @@ void drv_disable_wq(struct idxd_wq *wq) dev_warn(dev, "Clients has claim on wq %d: %d\n", wq->id, idxd_wq_refcount(wq));
- idxd_wq_free_resources(wq); idxd_wq_unmap_portal(wq); idxd_wq_drain(wq); idxd_wq_free_irq(wq); idxd_wq_reset(wq); + idxd_wq_free_resources(wq); percpu_ref_exit(&wq->wq_active); wq->type = IDXD_WQT_NONE; wq->client_count = 0;