linux-kernel - Re: [PATCH RESEND v4] perf record: Fix segfault with --overwrite and --max-size

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Date:   Wed, 15 Feb 2023 10:22:27 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Yang Jihong <yangjihong1@...wei.com>
Cc:     peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org, jiwei.sun@...driver.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v4] perf record: Fix segfault with --overwrite and
 --max-size

Em Wed, Feb 15, 2023 at 12:23:24PM +0000, Yang Jihong escreveu:
> When --overwrite and --max-size options of perf record are used together,
> a segmentation fault occurs. The following is an example:
<SNIP>
> We add a member variable "thread_bytes_written" in the struct "record"
> to save the data size written by the threads.
> 
> Fixes: 6d57581659f7 ("perf record: Add support for limit perf output file size")
> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
> Acked-by: Namhyung Kim <namhyung@...nel.org>
> ---
> 
> Changes since v3:
>  - Add Namhyung Kim Acked-by
>    (I don't know whether the problem is caused by my email address, Send again)

Thanks, applied.

- Arnaldo

 
> Changes since v2:
>  - Save data size written by threads to calculate the correct total data size.
>  - Update commit message.
> 
> Changes since v1:
>  - Add variable check in record__bytes_written for code hardening.
>  - Save bytes_written separately to reduce one calculation.
>  - Remove rec->opts.tail_synthesize check.
> 
>  tools/perf/builtin-record.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 29dcd454b8e2..8374117e66f6 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -154,6 +154,7 @@ struct record {
>  	struct perf_tool	tool;
>  	struct record_opts	opts;
>  	u64			bytes_written;
> +	u64			thread_bytes_written;
>  	struct perf_data	data;
>  	struct auxtrace_record	*itr;
>  	struct evlist	*evlist;
> @@ -226,14 +227,7 @@ static bool switch_output_time(struct record *rec)
>  
>  static u64 record__bytes_written(struct record *rec)
>  {
> -	int t;
> -	u64 bytes_written = rec->bytes_written;
> -	struct record_thread *thread_data = rec->thread_data;
> -
> -	for (t = 0; t < rec->nr_threads; t++)
> -		bytes_written += thread_data[t].bytes_written;
> -
> -	return bytes_written;
> +	return rec->bytes_written + rec->thread_bytes_written;
>  }
>  
>  static bool record__output_max_size_exceeded(struct record *rec)
> @@ -255,10 +249,12 @@ static int record__write(struct record *rec, struct mmap *map __maybe_unused,
>  		return -1;
>  	}
>  
> -	if (map && map->file)
> +	if (map && map->file) {
>  		thread->bytes_written += size;
> -	else
> +		rec->thread_bytes_written += size;
> +	} else {
>  		rec->bytes_written += size;
> +	}
>  
>  	if (record__output_max_size_exceeded(rec) && !done) {
>  		fprintf(stderr, "[ perf record: perf size limit reached (%" PRIu64 " KB),"
> -- 
> 2.30.GIT
> 

-- 

- Arnaldo