6.6-stable review patch. If anyone has any objections, please let me know.
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From: Qiu-ji Chen chenqiuji666@gmail.com
commit 91d44c1afc61a2fec37a9c7a3485368309391e0b upstream.
Fixed a possible UAF problem in driver_override_show() in drivers/cdx/cdx.c
This function driver_override_show() is part of DEVICE_ATTR_RW, which includes both driver_override_show() and driver_override_store(). These functions can be executed concurrently in sysfs.
The driver_override_store() function uses driver_set_override() to update the driver_override value, and driver_set_override() internally locks the device (device_lock(dev)). If driver_override_show() reads cdx_dev->driver_override without locking, it could potentially access a freed pointer if driver_override_store() frees the string concurrently. This could lead to printing a kernel address, which is a security risk since DEVICE_ATTR can be read by all users.
Additionally, a similar pattern is used in drivers/amba/bus.c, as well as many other bus drivers, where device_lock() is taken in the show function, and it has been working without issues.
This potential bug was detected by our experimental static analysis tool, which analyzes locking APIs and paired functions to identify data races and atomicity violations.
Fixes: 1f86a00c1159 ("bus/fsl-mc: add support for 'driver_override' in the mc-bus") Cc: stable stable@kernel.org Signed-off-by: Qiu-ji Chen chenqiuji666@gmail.com Link: https://lore.kernel.org/r/20250118070833.27201-1-chenqiuji666@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/cdx/cdx.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/drivers/cdx/cdx.c +++ b/drivers/cdx/cdx.c @@ -365,8 +365,12 @@ static ssize_t driver_override_show(stru 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);