Messages in this thread | | | Date | Tue, 24 May 2022 12:40:41 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH -next] cpufreq: Fix reserved space in cpufreq_show_cpus() |
| |
On 21-05-22, 14:35, Yi Yang wrote: > Function scnprintf() would reserve space for the trailing '\0' and return > value is the number of characters written into buf not including the > trailing '\0'. internally meaning the next scnprintf() would write begin > the trailing '\0'. The code specifying "PAGE_SIZE - i - 2" here is trying > to reserve space for "\n\0" which would cause scnprintf() to reserve an > additional byte making the tail of the buf looks like this: "\n\0\0". > Thus. we should reserve only the space for one '\0'. passing in > "PAGE_SIZE - i - 1". > > Additionally, each iteration would replace the trailing '\0' from the last > iteration with a space, and append 4 additional bytes to the string making > it a total of 5 additional bytes. That means we should stop printing into > the buffer if the remaining size is less than 7 bytes(1 for the ' ', 4 for > the %u and 2 for the tailing "\n\0") > > Signed-off-by: Yi Yang <yiyang13@huawei.com> > --- > drivers/cpufreq/cpufreq.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index 1f6667ce43bd..60c005c9961e 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -844,9 +844,9 @@ ssize_t cpufreq_show_cpus(const struct cpumask *mask, char *buf) > > for_each_cpu(cpu, mask) { > if (i) > - i += scnprintf(&buf[i], (PAGE_SIZE - i - 2), " "); > - i += scnprintf(&buf[i], (PAGE_SIZE - i - 2), "%u", cpu); > - if (i >= (PAGE_SIZE - 5)) > + i += scnprintf(&buf[i], (PAGE_SIZE - i - 1), " "); > + i += scnprintf(&buf[i], (PAGE_SIZE - i - 1), "%u", cpu); > + if (i >= (PAGE_SIZE - 6)) > break; > } > i += sprintf(&buf[i], "\n");
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
-- viresh
| |