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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Song Liu <songliubraving@fb.com>,
        Peter Zijlstra <peterz@infradead.org>, kernel-team@fb.com,
        Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: [PATCH 5.10 77/77] perf script: Check session->header.env.arch before using it
Date:   Mon,  1 Nov 2021 10:18:05 +0100
Message-Id: <20211101082527.560848483@linuxfoundation.org>
In-Reply-To: <20211101082511.254155853@linuxfoundation.org>
References: <20211101082511.254155853@linuxfoundation.org>
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From: Song Liu <songliubraving@fb.com>

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

--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -3820,11 +3820,15 @@ int cmd_script(int argc, const char **ar
 		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);