linux-kernel - Re: [PATCH v2 2/3] tracing: Fix parse_synth

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Message-Id: <20201001142723.66b8f3d7d6f7df803044c567@kernel.org>
Date:   Thu, 1 Oct 2020 14:27:23 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Tom Zanussi <zanussi@...nel.org>
Cc:     rostedt@...dmis.org, axelrasmussen@...gle.com, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] tracing: Fix parse_synth_field() error handling

Hi Tom,

On Wed, 30 Sep 2020 13:40:51 -0500
Tom Zanussi <zanussi@...nel.org> wrote:

> synth_field_size() returns either a positive size or an error (zero or
> a negative value). However, the existing code assumes the only error
> value is 0. It doesn't handle negative error codes, as it assigns
> directly to field->size (a size_t; unsigned), thereby interpreting the
> error code as a valid size instead.
> 
> Do the test before assignment to field->size.

This looks good to me. And I guess it is a kind of bugfix which should be backported?
(doesn't this need a Fixes tag?)

Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you,

> 
> [ axelrasmussen@...gle.com: changelog addition, first paragraph above ]
> 
> Signed-off-by: Tom Zanussi <zanussi@...nel.org>
> ---
>  kernel/trace/trace_events_synth.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> index a9cd7793f7ea..fa8a99828f41 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -465,6 +465,7 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
>  	struct synth_field *field;
>  	const char *prefix = NULL, *field_type = argv[0], *field_name, *array;
>  	int len, ret = 0;
> +	ssize_t size;
>  
>  	if (field_type[0] == ';')
>  		field_type++;
> @@ -520,11 +521,12 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
>  			field->type[len - 1] = '\0';
>  	}
>  
> -	field->size = synth_field_size(field->type);
> -	if (!field->size) {
> +	size = synth_field_size(field->type);
> +	if (size <= 0) {
>  		ret = -EINVAL;
>  		goto free;
>  	}
> +	field->size = size;
>  
>  	if (synth_field_is_string(field->type))
>  		field->is_string = true;
> -- 
> 2.17.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>