When a driver is probed through __driver_attach(), the bus' match() callback is called without the device lock held, thus accessing the driver_override field without a lock, which can cause a UAF.
Fix this by using the driver-core driver_override infrastructure taking care of proper locking internally. Note that calling match() from __driver_attach() without the device lock held is intentional. [1] Link: https://lore.kernel.org/driver-core/[email protected]/ [1] Reported-by: Gui-Dong Han <[email protected]> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789 Fixes: 1f86a00c1159 ("bus/fsl-mc: add support for 'driver_override' in the mc-bus") Signed-off-by: Danilo Krummrich <[email protected]> --- drivers/bus/fsl-mc/fsl-mc-bus.c | 43 +++++-------------------------- drivers/vfio/fsl-mc/vfio_fsl_mc.c | 4 +-- include/linux/fsl/mc.h | 4 --- 3 files changed, 8 insertions(+), 43 deletions(-) diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c index c117745cf206..221146e4860b 100644 --- a/drivers/bus/fsl-mc/fsl-mc-bus.c +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c @@ -86,12 +86,16 @@ static int fsl_mc_bus_match(struct device *dev, const struct device_driver *drv) struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev); const struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(drv); bool found = false; + int ret; /* When driver_override is set, only bind to the matching driver */ - if (mc_dev->driver_override) { - found = !strcmp(mc_dev->driver_override, mc_drv->driver.name); + ret = device_match_driver_override(dev, drv); + if (ret > 0) { + found = true; goto out; } + if (ret == 0) + goto out; if (!mc_drv->match_id_table) goto out; @@ -210,39 +214,8 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR_RO(modalias); -static ssize_t driver_override_store(struct device *dev, - struct device_attribute *attr, - const char *buf, size_t count) -{ - struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev); - int ret; - - if (WARN_ON(dev->bus != &fsl_mc_bus_type)) - return -EINVAL; - - ret = driver_set_override(dev, &mc_dev->driver_override, buf, count); - if (ret) - return ret; - - return count; -} - -static ssize_t driver_override_show(struct device *dev, - struct device_attribute *attr, char *buf) -{ - struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev); - ssize_t len; - - device_lock(dev); - len = sysfs_emit(buf, "%s\n", mc_dev->driver_override); - device_unlock(dev); - return len; -} -static DEVICE_ATTR_RW(driver_override); - static struct attribute *fsl_mc_dev_attrs[] = { &dev_attr_modalias.attr, - &dev_attr_driver_override.attr, NULL, }; @@ -345,6 +318,7 @@ ATTRIBUTE_GROUPS(fsl_mc_bus); const struct bus_type fsl_mc_bus_type = { .name = "fsl-mc", + .driver_override = true, .match = fsl_mc_bus_match, .uevent = fsl_mc_bus_uevent, .probe = fsl_mc_probe, @@ -910,9 +884,6 @@ static struct notifier_block fsl_mc_nb; */ void fsl_mc_device_remove(struct fsl_mc_device *mc_dev) { - kfree(mc_dev->driver_override); - mc_dev->driver_override = NULL; - /* * The device-specific remove callback will get invoked by device_del() */ diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c index 462fae1aa538..b4c3958201b2 100644 --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c @@ -424,9 +424,7 @@ static int vfio_fsl_mc_bus_notifier(struct notifier_block *nb, if (action == BUS_NOTIFY_ADD_DEVICE && vdev->mc_dev == mc_cont) { - mc_dev->driver_override = kasprintf(GFP_KERNEL, "%s", - vfio_fsl_mc_ops.name); - if (!mc_dev->driver_override) + if (device_set_driver_override(dev, vfio_fsl_mc_ops.name)) dev_warn(dev, "VFIO_FSL_MC: Setting driver override for device in dprc %s failed\n", dev_name(&mc_cont->dev)); else diff --git a/include/linux/fsl/mc.h b/include/linux/fsl/mc.h index 897d6211c163..1da63f2d7040 100644 --- a/include/linux/fsl/mc.h +++ b/include/linux/fsl/mc.h @@ -178,9 +178,6 @@ struct fsl_mc_obj_desc { * @regions: pointer to array of MMIO region entries * @irqs: pointer to array of pointers to interrupts allocated to this device * @resource: generic resource associated with this MC object device, if any. - * @driver_override: driver name to force a match; do not set directly, - * because core frees it; use driver_set_override() to - * set or clear it. * * Generic device object for MC object devices that are "attached" to a * MC bus. @@ -214,7 +211,6 @@ struct fsl_mc_device { struct fsl_mc_device_irq **irqs; struct fsl_mc_resource *resource; struct device_link *consumer_link; - const char *driver_override; }; #define to_fsl_mc_device(_dev) \ -- 2.53.0
