diff options
| author | Robin Murphy <robin.murphy@arm.com> | 2025-04-25 16:39:28 +0300 |
|---|---|---|
| committer | Christophe Leroy <christophe.leroy@csgroup.eu> | 2025-05-13 02:38:55 +0300 |
| commit | 152f33ee30ee6a7f4c15bedd7529dc5945315547 (patch) | |
| tree | 8088db3d2aa80acaffd9acbfbdaa9586a5c2d7b4 | |
| parent | 23d060136841c58c2f9ee8c08ad945d1879ead4b (diff) | |
| download | linux-152f33ee30ee6a7f4c15bedd7529dc5945315547.tar.xz | |
bus: fsl_mc: Fix driver_managed_dma check
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
TOCTOU issue, where dev->driver becomes valid after to_fsl_mc_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.
Reported-by: Will McVicker <willmcvicker@google.com>
Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper probe path")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Will McVicker <willmcvicker@google.com>
Link: https://lore.kernel.org/r/20250425133929.646493-3-robin.murphy@arm.com
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
| -rw-r--r-- | drivers/bus/fsl-mc/fsl-mc-bus.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c index 0c3a38d7f335..7671bd158545 100644 --- a/drivers/bus/fsl-mc/fsl-mc-bus.c +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c @@ -139,9 +139,9 @@ static int fsl_mc_bus_uevent(const struct device *dev, struct kobj_uevent_env *e static int fsl_mc_dma_configure(struct device *dev) { + const struct device_driver *drv = READ_ONCE(dev->driver); struct device *dma_dev = dev; struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev); - struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(dev->driver); u32 input_id = mc_dev->icid; int ret; @@ -153,8 +153,8 @@ static int fsl_mc_dma_configure(struct device *dev) else ret = acpi_dma_configure_id(dev, DEV_DMA_COHERENT, &input_id); - /* @mc_drv may not be valid when we're called from the IOMMU layer */ - if (!ret && dev->driver && !mc_drv->driver_managed_dma) { + /* @drv may not be valid when we're called from the IOMMU layer */ + if (!ret && drv && !to_fsl_mc_driver(drv)->driver_managed_dma) { ret = iommu_device_use_default_domain(dev); if (ret) arch_teardown_dma_ops(dev); |