linux-kernel - Re: [PATCH] function_graph: Fix off-by-one error in buffer size

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Message-ID: <20250617110017.2883cba3@gandalf.local.home>
Date: Tue, 17 Jun 2025 11:00:17 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Artem Sadovnikov <a.sadovnikov@...ras.ru>
Cc: linux-kernel@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
 lvc-project@...uxtesting.org
Subject: Re: [PATCH] function_graph: Fix off-by-one error in buffer size

On Tue, 17 Jun 2025 11:19:06 +0000
Artem Sadovnikov <a.sadovnikov@...ras.ru> wrote:

> The comment above buffer mentions sign, 10 bytes width for number and null
> terminator, but buffer itself isn't large enough to hold that much data.
> 
> This is a cosmetic change, since PID cannot be negative, other than -1.

Right, where I'll change the subject as that makes it look like this is a
real bug.

And it is likely that "pid_str" will be allocated as 12 anyway, just for
alignment reasons. But I'll take your patch.

-- Steve


> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Artem Sadovnikov <a.sadovnikov@...ras.ru>
> ---
>  kernel/trace/trace_functions_graph.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index a8c1f56340680..d789d308ab1de 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -344,7 +344,7 @@ static void print_graph_proc(struct trace_seq *s, pid_t pid)
>  {
>  	char comm[TASK_COMM_LEN];
>  	/* sign + log10(MAX_INT) + '\0' */
> -	char pid_str[11];
> +	char pid_str[12];
>  	int spaces = 0;
>  	int len;
>  	int i;