On Wed, Jul 6, 2022 at 8:45 AM Greg KH gregkh@linuxfoundation.org wrote:
On Tue, Jul 05, 2022 at 11:02:50PM +0200, Varad Gautam wrote:
On Tue, Jul 5, 2022 at 6:18 PM Greg KH gregkh@linuxfoundation.org wrote:
On Tue, Jul 05, 2022 at 03:00:02PM +0000, Varad Gautam wrote:
Check that a user-provided thermal state is within the maximum thermal states supported by a given driver before attempting to apply it. This prevents a subsequent OOB access in thermal_cooling_device_stats_update() while performing state-transition accounting on drivers that do not have this check in their set_cur_state() handle.
Signed-off-by: Varad Gautam varadgautam@google.com Cc: stable@vger.kernel.org
drivers/thermal/thermal_sysfs.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c index 1c4aac8464a7..0c6b0223b133 100644 --- a/drivers/thermal/thermal_sysfs.c +++ b/drivers/thermal/thermal_sysfs.c @@ -607,7 +607,7 @@ cur_state_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { struct thermal_cooling_device *cdev = to_cooling_device(dev);
unsigned long state;
unsigned long state, max_state; int result; if (sscanf(buf, "%ld\n", &state) != 1)@@ -618,10 +618,20 @@ cur_state_store(struct device *dev, struct device_attribute *attr,
mutex_lock(&cdev->lock);
result = cdev->ops->get_max_state(cdev, &max_state);if (result)goto unlock;if (state > max_state) {result = -EINVAL;goto unlock;}result = cdev->ops->set_cur_state(cdev, state);Why doesn't set_cur_state() check the max state before setting it? Why are the callers forced to always check it before? That feels wrong...
The problem lies in thermal_cooling_device_stats_update(), not set_cur_state().
If ->set_cur_state() doesn't error out on invalid state, thermal_cooling_device_stats_update() does a:
stats->trans_table[stats->state * stats->max_states + new_state]++;
stats->trans_table reserves space depending on max_states, but we'd end up reading/writing outside it. cur_state_store() can prevent this regardless of the driver's ->set_cur_state() implementation.
Why wouldn't cur_state_store() check for an out-of-bounds condition by calling get_max_state() and then return an error if it is invalid, preventing thermal_cooling_device_stats_update() from ever being called?
That's what this patch does, it adds the out-of-bounds check.
thanks,
greg k-h