linux-kernel - [PATCH] perf: fix segfault when wrong option for --debug is provided

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Message-Id: <20210531212828.240077-1-rickyman7@gmail.com>
Date:   Mon, 31 May 2021 23:28:28 +0200
From:   Riccardo Mancini <rickyman7@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>
Cc:     Riccardo Mancini <rickyman7@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] perf: fix segfault when wrong option for --debug is provided

The command `perf --debug record` causes a segfault instead of notifying
the user of the unrecognized option for --debug (the correct syntax would
be `perf --debug verbose=2 record`).

The bug is caused by a call to pr_err before debug_file (debug.c:34) is
set via perf_debug_setup(). It has been introduced in
commit 8abceacff87d ("perf debug: Add debug_set_file function").

This patch resolves the bug by calling perf_debug_setup earlier in the
main, so that debug_file is set to stderr before any call to a debug
printing function is made.

Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
---
 tools/perf/perf.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 20cb91ef06ffc..cffbab2d085a7 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -448,6 +448,7 @@ int main(int argc, const char **argv)
 	pager_init(PERF_PAGER_ENVIRONMENT);
 
 	libperf_init(libperf_print);
+	perf_debug_setup();
 
 	cmd = extract_argv0_path(argv[0]);
 	if (!cmd)
@@ -531,8 +532,6 @@ int main(int argc, const char **argv)
 	 */
 	pthread__block_sigwinch();
 
-	perf_debug_setup();
-
 	while (1) {
 		static int done_help;
 
-- 
2.23.0