[PATCH AUTOSEL 5.15 02/19] PCI: switchtec: Fix stdev_release() crash after surprise hot remove

Sasha Levin
2024-01-28T16:15:28Z

From: Daniel Stodden <dns@arista.com>

[ Upstream commit df25461119d987b8c81d232cfe4411e91dcabe66 ]

A PCI device hot removal may occur while stdev->cdev is held open. The call
to stdev_release() then happens 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 devm cleanup has already removed the
stdev->mmio_mrpc mapping. 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.

Fix 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.

Reproducible via the script at
https://lore.kernel.org/r/20231113212150.96410-1-dns@arista.com

Link: https://lore.kernel.org/r/20231122042316.91208-2-dns@arista.com
Signed-off-by: Daniel Stodden <dns@arista.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/switch/switchtec.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
index d021ef3fb165..2a026183f06b 100644
--- a/drivers/pci/switch/switchtec.c
+++ b/drivers/pci/switch/switchtec.c
@@ -1250,13 +1250,6 @@ 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);
}

@@ -1300,7 +1293,7 @@ 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;
@@ -1334,6 +1327,7 @@ static struct switchtec_dev *stdev_create(struct pci_dev *pdev)
return stdev;

err_put:
+ pci_dev_put(stdev->pdev);
put_device(&stdev->dev);
return ERR_PTR(rc);
}
@@ -1586,6 +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)
{
@@ -1645,6 +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);
}

--
2.43.0