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SubjectRe: [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

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