6.15-stable review patch. If anyone has any objections, please let me know.
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From: Robin Murphy robin.murphy@arm.com
[ Upstream commit 78447d4545b2ea76ee04f4e46d473639483158b2 ]
Since it's not currently safe to take device_lock() in the IOMMU probe path, that can race against really_probe() setting dev->driver before attempting to bind. The race itself isn't so bad, since we're only concerned with dereferencing dev->driver itself anyway, but sadly my attempt to implement the check with minimal churn leads to a kind of Time-of-Check to Time-of-Use (TOCTOU) issue, where dev->driver becomes valid after to_pci_driver(NULL) is already computed, and thus the check fails to work as intended.
Will and I both hit this with the platform bus, but the pattern here is the same, so fix it for correctness too.
Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper probe path") Reported-by: Will McVicker willmcvicker@google.com Signed-off-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Will McVicker willmcvicker@google.com Link: https://patch.msgid.link/20250425133929.646493-4-robin.murphy@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/pci-driver.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index c8bd71a739f7..66e3bea7dc1a 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -1634,7 +1634,7 @@ static int pci_bus_num_vf(struct device *dev) */ static int pci_dma_configure(struct device *dev) { - struct pci_driver *driver = to_pci_driver(dev->driver); + const struct device_driver *drv = READ_ONCE(dev->driver); struct device *bridge; int ret = 0;
@@ -1651,8 +1651,8 @@ static int pci_dma_configure(struct device *dev)
pci_put_host_bridge_device(bridge);
- /* @driver may not be valid when we're called from the IOMMU layer */ - if (!ret && dev->driver && !driver->driver_managed_dma) { + /* @drv may not be valid when we're called from the IOMMU layer */ + if (!ret && drv && !to_pci_driver(drv)->driver_managed_dma) { ret = iommu_device_use_default_domain(dev); if (ret) arch_teardown_dma_ops(dev);