perf script: Check session->header.env.arch before using it

When perf.data is not written cleanly, we would like to process existing
data as much as possible (please see f_header.data.size == 0 condition
in perf_session__read_header). However, perf.data with partial data may
crash perf. Specifically, we see crash in 'perf script' for NULL
session->header.env.arch.

Fix this by checking session->header.env.arch before using it to determine
native_arch. Also split the if condition so it is easier to read.

Committer notes:

If it is a pipe, we already assume is a native arch, so no need to check
session->header.env.arch.

Signed-off-by: Song Liu <songliubraving@fb.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team@fb.com
Cc: stable@vger.kernel.org
Link: http://lore.kernel.org/lkml/20211004053238.514936-1-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 6211d0b..42eb6bd 100644 (file)
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -4039,11 +4039,15 @@ script_found:
                goto out_delete;
 
        uname(&uts);
-       if (data.is_pipe ||  /* assume pipe_mode indicates native_arch */
-           !strcmp(uts.machine, session->header.env.arch) ||
-           (!strcmp(uts.machine, "x86_64") &&
-            !strcmp(session->header.env.arch, "i386")))
+       if (data.is_pipe) { /* Assume pipe_mode indicates native_arch */
                native_arch = true;
+       } else if (session->header.env.arch) {
+               if (!strcmp(uts.machine, session->header.env.arch))
+                       native_arch = true;
+               else if (!strcmp(uts.machine, "x86_64") &&
+                        !strcmp(session->header.env.arch, "i386"))
+                       native_arch = true;
+       }
 
        script.session = session;
        script__setup_sample_type(&script);