linux-kernel - Re: [PATCH v2] perf ioctl: Add check for the sample

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Date:   Mon, 17 Jun 2019 14:08:32 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     mpe@...erman.id.au, peterz@...radead.org
Cc:     jolsa@...hat.com, maddy@...ux.vnet.ibm.com, acme@...nel.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH v2] perf ioctl: Add check for the sample_period value

Peter / mpe,

Is the v2 looks good? If so, can anyone of you please pick this up.

On 6/4/19 9:59 AM, Ravi Bangoria wrote:
> perf_event_open() limits the sample_period to 63 bits. See
> commit 0819b2e30ccb ("perf: Limit perf_event_attr::sample_period
> to 63 bits"). Make ioctl() consistent with it.
> 
> Also on powerpc, negative sample_period could cause a recursive
> PMIs leading to a hang (reported when running perf-fuzzer).
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> ---
>  kernel/events/core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index abbd4b3b96c2..e44c90378940 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5005,6 +5005,9 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg)
>  	if (perf_event_check_period(event, value))
>  		return -EINVAL;
>  
> +	if (!event->attr.freq && (value & (1ULL << 63)))
> +		return -EINVAL;
> +
>  	event_function_call(event, __perf_event_period, &value);
>  
>  	return 0;
>