[PATCH 1/1] perf machine: Use path__join() to compose a path instead of snprintf(dir, '/', filename)

[PATCH 1/1] perf machine: Use path__join() to compose a path instead of snprintf(dir, '/', filename)

[Arnaldo Carvalho de Melo]

Its more intention revealing, and if we're interested in the odd cases
where this may end up truncating we can do debug checks at one
centralized place.

Motivation, of all the container builds, fedora rawhide started
complaining of:

  util/machine.c: In function ‘machine__create_modules’:
  util/machine.c:1419:50: error: ‘%s’ directive output may be truncated writing up to 255 bytes into a region of size between 0 and 4095 [-Werror=format-truncation=]
   1419 |                 snprintf(path, sizeof(path), "%s/%s", dir_name, dent->d_name);
        |                                                  ^~
  In file included from /usr/include/stdio.h:894,
                   from util/branch.h:9,
                   from util/callchain.h:8,
                   from util/machine.c:7:
  In function ‘snprintf’,
      inlined from ‘maps__set_modules_path_dir’ at util/machine.c:1419:3,
      inlined from ‘machine__set_modules_path’ at util/machine.c:1473:9,
      inlined from ‘machine__create_modules’ at util/machine.c:1519:7:
  /usr/include/bits/stdio2.h:71:10: note: ‘__builtin___snprintf_chk’ output between 2 and 4352 bytes into a destination of size 4096

There are other places where we should use path__join(), but lets get rid of
this one first.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/machine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3901440aeff92652..f70ba56912d4f9f8 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -16,6 +16,7 @@
 #include "map_symbol.h"
 #include "branch.h"
 #include "mem-events.h"
+#include "path.h"
 #include "srcline.h"
 #include "symbol.h"
 #include "sort.h"
@@ -1416,7 +1417,7 @@ static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, i
 		struct stat st;
 
 		/*sshfs might return bad dent->d_type, so we have to stat*/
-		snprintf(path, sizeof(path), "%s/%s", dir_name, dent->d_name);
+		path__join(path, sizeof(path), dir_name, dent->d_name);
 		if (stat(path, &st))
 			continue;
 
-- 
2.34.1

Re: [PATCH 1/1] perf machine: Use path__join() to compose a path instead of snprintf(dir, '/', filename)

[Ian Rogers]

On Tue, Jan 18, 2022 at 7:13 AM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Its more intention revealing, and if we're interested in the odd cases
> where this may end up truncating we can do debug checks at one
> centralized place.
>
> Motivation, of all the container builds, fedora rawhide started
> complaining of:
>
>   util/machine.c: In function ‘machine__create_modules’:
>   util/machine.c:1419:50: error: ‘%s’ directive output may be truncated writing up to 255 bytes into a region of size between 0 and 4095 [-Werror=format-truncation=]
>    1419 |                 snprintf(path, sizeof(path), "%s/%s", dir_name, dent->d_name);
>         |                                                  ^~
>   In file included from /usr/include/stdio.h:894,
>                    from util/branch.h:9,
>                    from util/callchain.h:8,
>                    from util/machine.c:7:
>   In function ‘snprintf’,
>       inlined from ‘maps__set_modules_path_dir’ at util/machine.c:1419:3,
>       inlined from ‘machine__set_modules_path’ at util/machine.c:1473:9,
>       inlined from ‘machine__create_modules’ at util/machine.c:1519:7:
>   /usr/include/bits/stdio2.h:71:10: note: ‘__builtin___snprintf_chk’ output between 2 and 4352 bytes into a destination of size 4096
>
> There are other places where we should use path__join(), but lets get rid of
> this one first.

Acked-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Ian Rogers <irogers@google.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/perf/util/machine.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 3901440aeff92652..f70ba56912d4f9f8 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -16,6 +16,7 @@
>  #include "map_symbol.h"
>  #include "branch.h"
>  #include "mem-events.h"
> +#include "path.h"
>  #include "srcline.h"
>  #include "symbol.h"
>  #include "sort.h"
> @@ -1416,7 +1417,7 @@ static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, i
>                 struct stat st;
>
>                 /*sshfs might return bad dent->d_type, so we have to stat*/
> -               snprintf(path, sizeof(path), "%s/%s", dir_name, dent->d_name);
> +               path__join(path, sizeof(path), dir_name, dent->d_name);
>                 if (stat(path, &st))
>                         continue;
>
> --
> 2.34.1
>