ACK: [SRU][Xenial][Artful][Bionic][PATCH 1/1] s390/cpum_sf: ensure sample frequency of perf event attributes is non-zero

[Stefan Bader]

On 25.05.2018 04:38, Joseph Salisbury wrote:
> From: Hendrik Brueckner <brueckner at linux.ibm.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1772593
> 
> Correct a trinity finding for the perf_event_open() system call with
> a perf event attribute structure that uses a frequency but has the
> sampling frequency set to zero.  This causes a FP divide exception during
> the sample rate initialization for the hardware sampling facility.
> 
> Fixes: 8c069ff4bd606 ("s390/perf: add support for the CPU-Measurement Sampling Facility")
> Cc: stable at vger.kernel.org # 3.14+
> Reviewed-by: Heiko Carstens <heiko.carstens at de.ibm.com>
> Signed-off-by: Hendrik Brueckner <brueckner at linux.ibm.com>
> Signed-off-by: Martin Schwidefsky <schwidefsky at de.ibm.com>
> (cherry picked from commit 4bbaf2584b86b0772413edeac22ff448f36351b1)
> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---
>  arch/s390/kernel/perf_cpum_sf.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
> index 3d8da1e..b79d514 100644
> --- a/arch/s390/kernel/perf_cpum_sf.c
> +++ b/arch/s390/kernel/perf_cpum_sf.c
> @@ -744,6 +744,10 @@ static int __hw_perf_event_init(struct perf_event *event)
>  	 */
>  	rate = 0;
>  	if (attr->freq) {
> +		if (!attr->sample_freq) {
> +			err = -EINVAL;
> +			goto out;
> +		}
>  		rate = freq_to_sample_rate(&si, attr->sample_freq);
>  		rate = hw_limit_rate(&si, rate);
>  		attr->freq = 0;
> 


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