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: ebc3d1791503 ("s390/cio: introduce driver_override on the css bus") Signed-off-by: Danilo Krummrich <[email protected]> --- drivers/s390/cio/cio.h | 5 ----- drivers/s390/cio/css.c | 34 ++++------------------------------ 2 files changed, 4 insertions(+), 35 deletions(-) diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h index 08a5e9380e75..bad142c536e1 100644 --- a/drivers/s390/cio/cio.h +++ b/drivers/s390/cio/cio.h @@ -103,11 +103,6 @@ struct subchannel { struct work_struct todo_work; struct schib_config config; u64 dma_mask; - /* - * Driver name to force a match. Do not set directly, because core - * frees it. Use driver_set_override() to set or clear it. - */ - const char *driver_override; } __attribute__ ((aligned(8))); DECLARE_PER_CPU_ALIGNED(struct irb, cio_irb); diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c index 5ab239f38588..e5a0ec6b4e3e 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -159,7 +159,6 @@ static void css_subchannel_release(struct device *dev) sch->config.intparm = 0; cio_commit_config(sch); - kfree(sch->driver_override); kfree(sch); } @@ -323,37 +322,9 @@ 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 subchannel *sch = to_subchannel(dev); - int ret; - - ret = driver_set_override(dev, &sch->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 subchannel *sch = to_subchannel(dev); - ssize_t len; - - device_lock(dev); - len = sysfs_emit(buf, "%s\n", sch->driver_override); - device_unlock(dev); - return len; -} -static DEVICE_ATTR_RW(driver_override); - static struct attribute *subch_attrs[] = { &dev_attr_type.attr, &dev_attr_modalias.attr, - &dev_attr_driver_override.attr, NULL, }; @@ -1356,9 +1327,11 @@ static int css_bus_match(struct device *dev, const struct device_driver *drv) struct subchannel *sch = to_subchannel(dev); const struct css_driver *driver = to_cssdriver(drv); struct css_device_id *id; + int ret; /* When driver_override is set, only bind to the matching driver */ - if (sch->driver_override && strcmp(sch->driver_override, drv->name)) + ret = device_match_driver_override(dev, drv); + if (ret == 0) return 0; for (id = driver->subchannel_type; id->match_flags; id++) { @@ -1415,6 +1388,7 @@ static int css_uevent(const struct device *dev, struct kobj_uevent_env *env) static const struct bus_type css_bus_type = { .name = "css", + .driver_override = true, .match = css_bus_match, .probe = css_probe, .remove = css_remove, -- 2.53.0
