[dpdk-dev] [PATCH] lib/power: fix governor storage to trim newlines

Burakov, Anatoly anatoly.burakov at intel.com
Fri Mar 29 17:25:47 CET 2019

On 29-Mar-19 4:11 PM, David Hunt wrote:
> Currently the Power Libray stores the governor name with an embedded
> newline read from the scaling_governor sysfs file. This patch strips
> it out.
> Fixes: 445c6528b55f ("power: common interface for guest and host")
> Cc: stable at dpdk.org
> Signed-off-by: David Hunt <david.hunt at intel.com>
> ---
>   lib/librte_power/power_acpi_cpufreq.c   | 4 ++++
>   lib/librte_power/power_pstate_cpufreq.c | 4 ++++
>   2 files changed, 8 insertions(+)
> diff --git a/lib/librte_power/power_acpi_cpufreq.c b/lib/librte_power/power_acpi_cpufreq.c
> index 45412f0b9..c2febdf06 100644
> --- a/lib/librte_power/power_acpi_cpufreq.c
> +++ b/lib/librte_power/power_acpi_cpufreq.c
> @@ -147,6 +147,10 @@ power_set_governor_userspace(struct rte_power_info *pi)
>   	s = fgets(buf, sizeof(buf), f);
>   	FOPS_OR_NULL_GOTO(s, out);
> +	buf[BUFSIZ-1] = '\0';
> +	if (strlen(buf))
> +		/* Strip off terminating '\n' */
> +		strtok(buf, "\n");

I have a feeling that either strlen or strtok here is unnecessary.

If it's always terminating - you can just use strlen return value and 
overwrite the '\n' without going over the string the second time - you 
know where the string ends!

You have already written null-terminator to the end of the buffer, so it 
can't overflow on strtok, so you don't really need strlen either, 
because the string will either:

1) be empty (in which case strtok does nothing)
2) contain text + newline (in which case you cut off the newline and 
leave the text - no need for strlen), or
3) contain just a newline (which would make it empty after strtok)

Did you mean to only cut off the newline off the strings that have stuff 
other than newline? That would be the only case where using strlen would 
make sense - in which case, not only the check is wrong, but you could 
also replace it with a simple 'if (buf[0] != '\n')' check instead of strlen.


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