From 669a7e147ee66ec42c36ddc99ae760c05bd1526c Mon Sep 17 00:00:00 2001
From: Song Liu <songliubraving@fb.com>
Date: Sun, 3 Oct 2021 22:32:38 -0700
Subject: [PATCH] perf script: Check session->header.env.arch before using it
Git-commit: 29c77550eef31b0d72a45b49eeab03b8963264e8
Patch-mainline: v5.15
References: stable-5.14.16

commit 29c77550eef31b0d72a45b49eeab03b8963264e8 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 tools/perf/builtin-script.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 52ff827ca799..6b6dbd84cdeb 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -4024,11 +4024,15 @@ int cmd_script(int argc, const char **argv)
 		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);
-- 
2.26.2