ACK: [PATCH] perf/core: Fix the perf_cpu_time_max_percent check

[Kleber Souza]

On 07/20/18 18:11, Colin King wrote:
> From: Tan Xiaojun <tanxiaojun at huawei.com>
> 
> CVE-2017-18255
> 
> Use "proc_dointvec_minmax" instead of "proc_dointvec" to check the input
> value from user-space.
> 
> If not, we can set a big value and some vars will overflow like
> "sysctl_perf_event_sample_rate" which will cause a lot of unexpected
> problems.
> 
> Signed-off-by: Tan Xiaojun <tanxiaojun at huawei.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
> Cc: <acme at kernel.org>
> Cc: <alexander.shishkin at linux.intel.com>
> Cc: Alexander Shishkin <alexander.shishkin at linux.intel.com>
> Cc: Arnaldo Carvalho de Melo <acme at redhat.com>
> Cc: Jiri Olsa <jolsa at redhat.com>
> Cc: Linus Torvalds <torvalds at linux-foundation.org>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: Stephane Eranian <eranian at google.com>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Vince Weaver <vincent.weaver at maine.edu>
> Link: http://lkml.kernel.org/r/1487829879-56237-1-git-send-email-tanxiaojun@huawei.com
> Signed-off-by: Ingo Molnar <mingo at kernel.org>
> (clean upstream cherry pick of commit 1572e45a924f254d9570093abde46430c3172e3d)
> Signed-off-by: Colin Ian King <colin.king at canonical.com>

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> ---
>  kernel/events/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index d4e3f8d..c1c1cdf 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -455,7 +455,7 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
>  				void __user *buffer, size_t *lenp,
>  				loff_t *ppos)
>  {
> -	int ret = proc_dointvec(table, write, buffer, lenp, ppos);
> +	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
>  
>  	if (ret || !write)
>  		return ret;
>