Messages in this thread | | | Date | Wed, 13 Jul 2022 14:07:09 +0530 | Subject | Re: [PATCH] PM: QoS: Add check to make sure CPU freq is non-negative | From | Shivnandan Kumar <> |
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Hi Rafael,
Thanks for taking the time to review my patch and providing feedback.
Please find answer inline.
Thanks,
Shivnandan
On 7/13/2022 12:07 AM, Rafael J. Wysocki wrote: > On Thu, Jun 23, 2022 at 8:47 AM Shivnandan Kumar > <quic_kshivnan@quicinc.com> wrote: >> CPU frequency should never be negative. > Do you mean "always be non-negative"? Yes,corrected subject now. > >> If some client driver calls freq_qos_update_request with some >> value greater than INT_MAX, then it will set max CPU freq at >> fmax but it will add plist node with some negative priority. >> plist node has priority from INT_MIN (highest) to INT_MAX >> (lowest). Once priority is set as negative, another client >> will not be able to reduce max CPU frequency. Adding check >> to make sure CPU freq is non-negative will fix this problem. >> Signed-off-by: Shivnandan Kumar <quic_kshivnan@quicinc.com> >> >> --- >> kernel/power/qos.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/power/qos.c b/kernel/power/qos.c >> index ec7e1e85923e..41e96fe34bfd 100644 >> --- a/kernel/power/qos.c >> +++ b/kernel/power/qos.c >> @@ -531,7 +531,8 @@ int freq_qos_add_request(struct freq_constraints *qos, >> { >> int ret; >> >> - if (IS_ERR_OR_NULL(qos) || !req) >> + if (IS_ERR_OR_NULL(qos) || !req || value < FREQ_QOS_MIN_DEFAULT_VALUE >> + || value > FREQ_QOS_MAX_DEFAULT_VALUE) > Why do you check against the defaults? Want to make sure to guard against negative value. > >> return -EINVAL; >> >> if (WARN(freq_qos_request_active(req), >> @@ -563,7 +564,8 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request); >> */ >> int freq_qos_update_request(struct freq_qos_request *req, s32 new_value) >> { >> - if (!req) >> + if (!req || new_value < FREQ_QOS_MIN_DEFAULT_VALUE || >> + new_value > FREQ_QOS_MAX_DEFAULT_VALUE) >> return -EINVAL; >> >> if (WARN(!freq_qos_request_active(req), >> -- > I agree that it should guard against adding negative values, but I > don't see why s32 can be greater than INT_MAX. yes, checking against negative values will be sufficient. I will share patch v2 with only check against negative values. > > Also why don't you put the guard into freq_qos_apply() instead of > duplicating it in the callers of that function? Because function freq_qos_remove_request calls freq_qos_apply with PM_QOS_DEFAULT_VALUE which is actually negative. So I do not want to break that.
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