linux-kernel - Re: [PATCH 2/5] perf tools kvm: Fix the potential out of range memory access issue

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Message-ID: <aJPrD_9J0SLiLFh9@google.com>
Date: Wed, 6 Aug 2025 16:53:51 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kevin Tian <kevin.tian@...el.com>, Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [PATCH 2/5] perf tools kvm: Fix the potential out of range
 memory access issue

On Tue, Aug 05, 2025 at 08:46:30AM +0800, Dapeng Mi wrote:
> kvm_add_default_arch_event() helper may add 2 extra options but it
> directly modifies the original argv[] array. This may cause out of range
> memory access. Fix this issue.
> 
> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
> ---
>  tools/perf/builtin-kvm.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> index f78a67a199ff..7e48d2437710 100644
> --- a/tools/perf/builtin-kvm.c
> +++ b/tools/perf/builtin-kvm.c
> @@ -2002,12 +2002,12 @@ static int __cmd_record(const char *file_name, int argc, const char **argv)
>  	int rec_argc, i = 0, j, ret;
>  	const char **rec_argv;
>  
> -	ret = kvm_add_default_arch_event(&argc, argv);
> -	if (ret)
> -		return -EINVAL;
> -
>  	rec_argc = argc + 2;

While at it, can we add a comment for this too?  I believe it's for "-o"
and filename.

Thanks,
Namhyung


> -	rec_argv = calloc(rec_argc + 1, sizeof(char *));
> +	/*
> +	 * kvm_add_default_arch_event() may add 2 extra options, so
> +	 * allocate 2 more pointers in adavance.
> +	 */
> +	rec_argv = calloc(rec_argc + 2 + 1, sizeof(char *));
>  	if (!rec_argv)
>  		return -ENOMEM;
>  
> @@ -2019,6 +2019,10 @@ static int __cmd_record(const char *file_name, int argc, const char **argv)
>  
>  	BUG_ON(i != rec_argc);
>  
> +	ret = kvm_add_default_arch_event(&i, rec_argv);
> +	if (ret)
> +		return -EINVAL;
> +
>  	ret = cmd_record(i, rec_argv);
>  	free(rec_argv);
>  	return ret;
> -- 
> 2.34.1
>