On Wed, Jul 6, 2022 at 11:21 AM Greg KH gregkh@linuxfoundation.org wrote:
On Wed, Jul 06, 2022 at 04:51:59PM +0800, Zhang Rui wrote:
On Wed, 2022-07-06 at 09:16 +0200, Varad Gautam wrote:
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.
No, I think Greg' question is why cdev->ops->set_cur_state() return 0 when setting a cooling state that exceeds the maximum cooling state?
Yes, that is what I am asking, it should not allow a state to be exceeded.
Indeed, it is upto the driver to return !0 from cdev->ops->set_cur_state() when setting state > max - and it is a driver bug for not doing so.
But a buggy driver should not lead to cur_state_store() performing an OOB access.
thanks,
greg k-h