linux-kernel - Re: [PATCH] [perf/core: Update sample_flags for raw_data in perf_output

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Date:   Thu, 20 Oct 2022 16:40:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
Cc:     acme@...nel.org, jolsa@...nel.org, namhyung@...nel.org,
        irogers@...gle.com, james.clark@....com, mpe@...erman.id.au,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, maddy@...ux.ibm.com,
        rnsastry@...ux.ibm.com, kjain@...ux.ibm.com, disgoel@...ux.ibm.com
Subject: Re: [PATCH] [perf/core: Update sample_flags for raw_data in
 perf_output_sample

On Thu, Oct 20, 2022 at 12:36:56PM +0530, Athira Rajeev wrote:
> commit 838d9bb62d13 ("perf: Use sample_flags for raw_data")
> added check for PERF_SAMPLE_RAW in sample_flags in
> perf_prepare_sample(). But while copying the sample in memory,
> the check for sample_flags is not added in perf_output_sample().
> Fix adds the same in perf_output_sample as well.
> 
> Fixes: 838d9bb62d13 ("perf: Use sample_flags for raw_data")
> Signed-off-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.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 4ec3717003d5..daf387c75d33 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7099,7 +7099,7 @@ void perf_output_sample(struct perf_output_handle *handle,
>  	if (sample_type & PERF_SAMPLE_RAW) {
>  		struct perf_raw_record *raw = data->raw;
>  
> -		if (raw) {
> +		if (raw && (data->sample_flags & PERF_SAMPLE_RAW)) {
>  			struct perf_raw_frag *frag = &raw->frag;
>  
>  			perf_output_put(handle, raw->size);

Urgh.. something smells here. We already did a PERF_SAMPLE_RAW test.

And perf_prepare_sample() explicitly makes data->raw be NULL when not
set earlier.

So what's going wrong?