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/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
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 <dakr@kernel.org>
---
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) \
--
2.53.0On Tue, Mar 24, 2026 at 01:59:06AM +0100, Danilo Krummrich wrote:
> 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/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
> Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
> 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 <dakr@kernel.org>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Le 25/03/2026 à 13:01, Ioana Ciornei a écrit :
> On Tue, Mar 24, 2026 at 01:59:06AM +0100, Danilo Krummrich wrote:
>> 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://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fdriver-core%2FDGRGTIRHA62X.3RY09D9SOK77P%40kernel.org%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4b9262ddecdd4ce29f9808de8a66485e%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639100369055903282%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=%2BRfjlUkq7oWV%2F0v2S2B%2BEuxCY%2FLRQv6qHiEWiupd6kc%3D&reserved=0 [1]
>> Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
>> Closes: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.kernel.org%2Fshow_bug.cgi%3Fid%3D220789&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4b9262ddecdd4ce29f9808de8a66485e%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639100369055936232%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=XL1K1ICiygOZnlvDUbQFe192KnLsBQms0HFNGCuyz%2Fw%3D&reserved=0
>> Fixes: 1f86a00c1159 ("bus/fsl-mc: add support for 'driver_override' in the mc-bus")
>> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
>
> Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
> Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
>
Applied, thanks
Le 28/03/2026 à 13:10, Christophe Leroy (CS GROUP) a écrit :
>
>
> Le 25/03/2026 à 13:01, Ioana Ciornei a écrit :
>> On Tue, Mar 24, 2026 at 01:59:06AM +0100, Danilo Krummrich wrote:
>>> 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://eur01.safelinks.protection.outlook.com/?
>>> url=https%3A%2F%2Flore.kernel.org%2Fdriver-
>>> core%2FDGRGTIRHA62X.3RY09D9SOK77P%40kernel.org%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4b9262ddecdd4ce29f9808de8a66485e%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639100369055903282%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=%2BRfjlUkq7oWV%2F0v2S2B%2BEuxCY%2FLRQv6qHiEWiupd6kc%3D&reserved=0 [1]
>>> Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
>>> Closes: https://eur01.safelinks.protection.outlook.com/?
>>> url=https%3A%2F%2Fbugzilla.kernel.org%2Fshow_bug.cgi%3Fid%3D220789&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4b9262ddecdd4ce29f9808de8a66485e%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639100369055936232%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=XL1K1ICiygOZnlvDUbQFe192KnLsBQms0HFNGCuyz%2Fw%3D&reserved=0
>>> Fixes: 1f86a00c1159 ("bus/fsl-mc: add support for 'driver_override'
>>> in the mc-bus")
>>> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
>>
>> Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
>> Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
>>
>
>
> Applied, thanks
Have to drop it for now, build fails:
CALL scripts/checksyscalls.sh
CC drivers/bus/fsl-mc/fsl-mc-bus.o
drivers/bus/fsl-mc/fsl-mc-bus.c: In function 'fsl_mc_bus_match':
drivers/bus/fsl-mc/fsl-mc-bus.c:92:15: error: implicit declaration of
function 'device_match_driver_override'
[-Werror=implicit-function-declaration]
92 | ret = device_match_driver_override(dev, drv);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/bus/fsl-mc/fsl-mc-bus.c: At top level:
drivers/bus/fsl-mc/fsl-mc-bus.c:321:10: error: 'const struct bus_type'
has no member named 'driver_override'
321 | .driver_override = true,
| ^~~~~~~~~~~~~~~
drivers/bus/fsl-mc/fsl-mc-bus.c:321:28: warning: initialization of
'const char *' from 'int' makes pointer from integer without a cast
[-Wint-conversion]
321 | .driver_override = true,
| ^~~~
drivers/bus/fsl-mc/fsl-mc-bus.c:321:28: note: (near initialization for
'fsl_mc_bus_type.dev_name')
cc1: some warnings being treated as errors
make[5]: *** [scripts/Makefile.build:289:
drivers/bus/fsl-mc/fsl-mc-bus.o] Error 1
make[4]: *** [scripts/Makefile.build:546: drivers/bus/fsl-mc] Error 2
make[3]: *** [scripts/Makefile.build:546: drivers/bus] Error 2
make[2]: *** [scripts/Makefile.build:546: drivers] Error 2
make[1]: *** [/home/chleroy/linux-powerpc/Makefile:2101: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2
Christophe
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