Re: [PATCH 05/10] rt-utils: Remove fileprefix.

[John Kacur <jkacur@redhat.com>]

On Wed, 3 Sep 2025, Sebastian Andrzej Siewior wrote:

> Remove fileprefix and use tracefs_prefix directly.
> There is no need for having both.
> Since sprintf() will complain that output buffer has the same size as
> the first input buffer so it could write more bytes use snprintf() and
> catch that possible overflow.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  src/lib/rt-utils.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/src/lib/rt-utils.c b/src/lib/rt-utils.c
> index 696bca2657d18..0e6e6056a4392 100644
> --- a/src/lib/rt-utils.c
> +++ b/src/lib/rt-utils.c
> @@ -33,7 +33,6 @@
>  #define  MAX_TS_SIZE 64
>  
>  static char tracefs_prefix[MAX_PATH];
> -static char *fileprefix;
>  static int trace_fd = -1;
>  static int tracemark_fd = -1;
>  static __thread char tracebuf[TRACEBUFSIZ];
> @@ -363,12 +362,17 @@ int parse_mem_string(char *str, uint64_t *val)
>  static void open_tracemark_fd(void)
>  {
>  	char path[MAX_PATH];
> +	int n;
>  
>  	/*
>  	 * open the tracemark file if it's not already open
>  	 */
>  	if (tracemark_fd < 0) {
> -		sprintf(path, "%s/%s", fileprefix, "trace_marker");
> +		n = snprintf(path, sizeof(path), "%s/%s", tracefs_prefix, "trace_marker");
> +		if (n >= sizeof(path)) {
> +			warn("tracefs path too long\n");
> +			return;
> +		}
>  		tracemark_fd = open(path, O_WRONLY);
>  		if (tracemark_fd < 0) {
>  			warn("unable to open trace_marker file: %s\n", path);
> @@ -382,7 +386,11 @@ static void open_tracemark_fd(void)
>  	 * if we hit a breaktrace threshold
>  	 */
>  	if (trace_fd < 0) {
> -		sprintf(path, "%s/%s", fileprefix, "tracing_on");
> +		n = snprintf(path, sizeof(path), "%s/%s", tracefs_prefix, "tracing_on");
> +		if (n >= sizeof(path)) {
> +			warn("tracefs path too long\n");
> +			return;
> +		}
>  		if ((trace_fd = open(path, O_WRONLY)) < 0)
>  			warn("unable to open tracing_on file: %s\n", path);
>  	}
> @@ -408,7 +416,7 @@ static int trace_file_exists(char *name)
>  
>  static void tracefs_prepare(void)
>  {
> -	fileprefix = get_tracefs_prefix();
> +	get_tracefs_prefix();
>  	if (!trace_file_exists("tracing_enabled") &&
>  	    !trace_file_exists("tracing_on"))
>  		warn("tracing_enabled or tracing_on not found\n"
> -- 
> 2.51.0
> 
> 
Signed-off-by: John Kacur <jkacur@redhat.com>