perf env: Do not return pointers to local variables

commit ebcb9464a2ae3a547e97de476575c82ece0e93e2 upstream.

It is possible to return a pointer to a local variable when looking up
the architecture name for the running system and no normalization is
done on that value, i.e. we may end up returning the uts.machine local
variable.

While this doesn't happen on most arches, as normalization takes place,
lets fix this by making that a static variable and optimize it a bit by
not always running uname(), only the first time.

Noticed in fedora rawhide running with:

  [perfbuilder@a5ff49d6e6e4 ~]$ gcc --version
  gcc (GCC) 10.0.1 20200216 (Red Hat 10.0.1-0.8)

Reported-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
index 3baca06786fb73494cd6e4b7d410b046dba63e6f..018ecf7b6da9b13b2c965f8eaa9e0da58b68317b 100644 (file)
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c
@@ -326,11 +326,11 @@ static const char *normalize_arch(char *arch)
 
 const char *perf_env__arch(struct perf_env *env)
 {
-       struct utsname uts;
        char *arch_name;
 
        if (!env || !env->arch) { /* Assume local operation */
-               if (uname(&uts) < 0)
+               static struct utsname uts = { .machine[0] = '\0', };
+               if (uts.machine[0] == '\0' && uname(&uts) < 0)
                        return NULL;
                arch_name = uts.machine;
        } else