perf string: Avoid undefined NULL+1

[PATCH v1] perf string: Avoid undefined NULL+1

Posted by Ian Rogers 1 year, 2 months ago

While the value NULL+1 is never used it triggers a ubsan
warning. Restructure and comment the loop to avoid this.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/string.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
index 308fc7ec88cc..c0e927bbadf6 100644
--- a/tools/perf/util/string.c
+++ b/tools/perf/util/string.c
@@ -254,11 +254,20 @@ char *strpbrk_esc(char *str, const char *stopset)
 
 	do {
 		ptr = strpbrk(str, stopset);
-		if (ptr == str ||
-		    (ptr == str + 1 && *(ptr - 1) != '\\'))
+		if (!ptr) {
+			/* stopset not in str. */
 			break;
+		}
+		if (ptr == str) {
+			/* stopset character is first in str. */
+			break;
+		}
+		if (ptr == str + 1 && str[0] != '\\') {
+			/* stopset chacter is second and wasn't preceded by a '\'. */
+			break;
+		}
 		str = ptr + 1;
-	} while (ptr && *(ptr - 1) == '\\' && *(ptr - 2) != '\\');
+	} while (ptr[-1] == '\\' && ptr[-2] != '\\');
 
 	return ptr;
 }
-- 
2.47.0.371.ga323438b13-goog

Re: [PATCH v1] perf string: Avoid undefined NULL+1

Posted by James Clark 1 year, 1 month ago


On 20/11/2024 6:52 am, Ian Rogers wrote:
> While the value NULL+1 is never used it triggers a ubsan
> warning. Restructure and comment the loop to avoid this.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>   tools/perf/util/string.c | 15 ++++++++++++---
>   1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
> index 308fc7ec88cc..c0e927bbadf6 100644
> --- a/tools/perf/util/string.c
> +++ b/tools/perf/util/string.c
> @@ -254,11 +254,20 @@ char *strpbrk_esc(char *str, const char *stopset)
>   
>   	do {
>   		ptr = strpbrk(str, stopset);
> -		if (ptr == str ||
> -		    (ptr == str + 1 && *(ptr - 1) != '\\'))
> +		if (!ptr) {
> +			/* stopset not in str. */
>   			break;
> +		}
> +		if (ptr == str) {
> +			/* stopset character is first in str. */
> +			break;
> +		}
> +		if (ptr == str + 1 && str[0] != '\\') {
> +			/* stopset chacter is second and wasn't preceded by a '\'. */
> +			break;
> +		}
>   		str = ptr + 1;
> -	} while (ptr && *(ptr - 1) == '\\' && *(ptr - 2) != '\\');
> +	} while (ptr[-1] == '\\' && ptr[-2] != '\\');
>   
>   	return ptr;
>   }

Reviewed-by: James Clark <james.clark@linaro.org>

Re: [PATCH v1] perf string: Avoid undefined NULL+1

Posted by Arnaldo Carvalho de Melo 1 year, 1 month ago

On Mon, Dec 09, 2024 at 11:49:15AM +0000, James Clark wrote:
> On 20/11/2024 6:52 am, Ian Rogers wrote:
> > While the value NULL+1 is never used it triggers a ubsan
> > warning. Restructure and comment the loop to avoid this.

> > Signed-off-by: Ian Rogers <irogers@google.com>
> > +++ b/tools/perf/util/string.c
> > @@ -254,11 +254,20 @@ char *strpbrk_esc(char *str, const char *stopset)
> >   	do {
> >   		ptr = strpbrk(str, stopset);
> > -		if (ptr == str ||
> > -		    (ptr == str + 1 && *(ptr - 1) != '\\'))
> > +		if (!ptr) {
> > +			/* stopset not in str. */
> >   			break;
> > +		}
> > +		if (ptr == str) {
> > +			/* stopset character is first in str. */
> > +			break;
> > +		}
> > +		if (ptr == str + 1 && str[0] != '\\') {
> > +			/* stopset chacter is second and wasn't preceded by a '\'. */
> > +			break;
> > +		}
> >   		str = ptr + 1;
> > -	} while (ptr && *(ptr - 1) == '\\' && *(ptr - 2) != '\\');
> > +	} while (ptr[-1] == '\\' && ptr[-2] != '\\');
> >   	return ptr;
> >   }
 
> Reviewed-by: James Clark <james.clark@linaro.org>

Thanks, applied to perf-tools-next,

- Arnaldo