There is a data race between the functions driver_override_show() and driver_override_store(). In the driver_override_store() function, the assignment to ret calls driver_set_override(), which frees the old value while writing the new value to dev. If a race occurs, it may cause a use-after-free (UAF) error in driver_override_show().
To fix this issue, we adopt a logic similar to the driver_override_show() function in vmbus_drv.c, protecting dev within a lock to ensure its value remains unchanged.
This possible bug is found by an experimental static analysis tool developed by our team. This tool analyzes the locking APIs to extract function pairs that can be concurrently executed, and then analyzes the instructions in the paired functions to identify possible concurrency bugs including data races and atomicity violations.
Fixes: 48a6c7bced2a ("cdx: add device attributes") Cc: stable@vger.kernel.org Signed-off-by: Qiu-ji Chen chenqiuji666@gmail.com --- V2: Modified the title and description. Removed the changes to cdx_bus_match(). --- drivers/cdx/cdx.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c index 07371cb653d3..4af1901c9d52 100644 --- a/drivers/cdx/cdx.c +++ b/drivers/cdx/cdx.c @@ -470,8 +470,12 @@ static ssize_t driver_override_show(struct device *dev, struct device_attribute *attr, char *buf) { struct cdx_device *cdx_dev = to_cdx_device(dev); + ssize_t len;
- return sysfs_emit(buf, "%s\n", cdx_dev->driver_override); + device_lock(dev); + len = sysfs_emit(buf, "%s\n", cdx_dev->driver_override); + device_unlock(dev); + return len; } static DEVICE_ATTR_RW(driver_override);
On Wed, Nov 13, 2024 at 12:23:38AM +0800, Qiu-ji Chen wrote:
There is a data race between the functions driver_override_show() and driver_override_store(). In the driver_override_store() function, the assignment to ret calls driver_set_override(), which frees the old value while writing the new value to dev. If a race occurs, it may cause a use-after-free (UAF) error in driver_override_show().
To fix this issue, we adopt a logic similar to the driver_override_show() function in vmbus_drv.c, protecting dev within a lock to ensure its value remains unchanged.
This possible bug is found by an experimental static analysis tool developed by our team. This tool analyzes the locking APIs to extract function pairs that can be concurrently executed, and then analyzes the instructions in the paired functions to identify possible concurrency bugs including data races and atomicity violations.
Fixes: 48a6c7bced2a ("cdx: add device attributes") Cc: stable@vger.kernel.org Signed-off-by: Qiu-ji Chen chenqiuji666@gmail.com
V2: Modified the title and description. Removed the changes to cdx_bus_match().
drivers/cdx/cdx.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c index 07371cb653d3..4af1901c9d52 100644 --- a/drivers/cdx/cdx.c +++ b/drivers/cdx/cdx.c @@ -470,8 +470,12 @@ static ssize_t driver_override_show(struct device *dev, struct device_attribute *attr, char *buf) { struct cdx_device *cdx_dev = to_cdx_device(dev);
- ssize_t len;
- return sysfs_emit(buf, "%s\n", cdx_dev->driver_override);
- device_lock(dev);
- len = sysfs_emit(buf, "%s\n", cdx_dev->driver_override);
- device_unlock(dev);
No, you should not need to lock a device in a sysfs callback like this, especially for just printing out a string.
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Qiu-ji Chen