On 11/13/23 21:21, Daniel Stodden wrote: > A pci device hot removal may occur while stdev->cdev is held open. The > call to stdev_release is then delivered during close or exit, at a > point way past switchtec_pci_remove. Otherwise the last ref would > vanish with the trailing put_device, just before return. > > At that later point in time, the device layer has alreay removed > stdev->mrpc_mmio map. Also, the stdev->pdev reference was not a > counted one. Therefore, in dma mode, the iowrite32 in stdev_release > will cause a fatal page fault, and the subsequent dma_free_coherent, > if reached, would pass a stale &stdev->pdev->dev pointer. > > Fixed by moving mrpc dma shutdown into switchtec_pci_remove, after > stdev_kill. Counting the stdev->pdev ref is now optional, but may > prevent future accidents. > > Signed-off-by: Daniel Stodden <dns@xxxxxxxxxx> > Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Just in case, duplicating on the patch. With pci_dev_put(stdev->pdev) on stdev_create() err-path, Reviewed-by: Dmitry Safonov <dima@xxxxxxxxxx> > --- > drivers/pci/switch/switchtec.c | 24 ++++++++++++++++-------- > 1 file changed, 16 insertions(+), 8 deletions(-) > > diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c > index e69cac84b605..d8718acdb85f 100644 > --- a/drivers/pci/switch/switchtec.c > +++ b/drivers/pci/switch/switchtec.c > @@ -1251,13 +1251,6 @@ static void stdev_release(struct device *dev) > { > struct switchtec_dev *stdev = to_stdev(dev); > > - if (stdev->dma_mrpc) { > - iowrite32(0, &stdev->mmio_mrpc->dma_en); > - flush_wc_buf(stdev); > - writeq(0, &stdev->mmio_mrpc->dma_addr); > - dma_free_coherent(&stdev->pdev->dev, sizeof(*stdev->dma_mrpc), > - stdev->dma_mrpc, stdev->dma_mrpc_dma_addr); > - } > kfree(stdev); > } > > @@ -1301,7 +1294,7 @@ static struct switchtec_dev *stdev_create(struct pci_dev *pdev) > return ERR_PTR(-ENOMEM); > > stdev->alive = true; > - stdev->pdev = pdev; > + stdev->pdev = pci_dev_get(pdev); > INIT_LIST_HEAD(&stdev->mrpc_queue); > mutex_init(&stdev->mrpc_mutex); > stdev->mrpc_busy = 0; > @@ -1587,6 +1580,18 @@ static int switchtec_init_pci(struct switchtec_dev *stdev, > return 0; > } > > +static void switchtec_exit_pci(struct switchtec_dev *stdev) > +{ > + if (stdev->dma_mrpc) { > + iowrite32(0, &stdev->mmio_mrpc->dma_en); > + flush_wc_buf(stdev); > + writeq(0, &stdev->mmio_mrpc->dma_addr); > + dma_free_coherent(&stdev->pdev->dev, sizeof(*stdev->dma_mrpc), > + stdev->dma_mrpc, stdev->dma_mrpc_dma_addr); > + stdev->dma_mrpc = NULL; > + } > +} > + > static int switchtec_pci_probe(struct pci_dev *pdev, > const struct pci_device_id *id) > { > @@ -1646,6 +1651,9 @@ static void switchtec_pci_remove(struct pci_dev *pdev) > ida_simple_remove(&switchtec_minor_ida, MINOR(stdev->dev.devt)); > dev_info(&stdev->dev, "unregistered.\n"); > stdev_kill(stdev); > + switchtec_exit_pci(stdev); > + pci_dev_put(stdev->pdev); > + stdev->pdev = NULL; > put_device(&stdev->dev); > } > Thanks, Dmitry