linux-kernel - [PATCH 1/1] perf top: Don't pass an ERR_PTR() directly to perf_session_

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Message-ID: <ZN4Q2rxxsL08A8rd@kernel.org>
Date:   Thu, 17 Aug 2023 09:21:46 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>,
        Mamatha Inamdar <mamatha4@...ux.vnet.ibm.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jeremie Galarneau <jeremie.galarneau@...icios.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mukesh Ojha <mojha@...eaurora.org>,
        Nageswara R Sastry <rnsastry@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Shawn Landden <shawn@....icu>,
        Song Liu <songliubraving@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tzvetomir Stoyanov <tstoyanov@...are.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/1] perf top: Don't pass an ERR_PTR() directly to
 perf_session__delete()

While debugging a segfault on 'perf lock contention' without an
available perf.data file I noticed that it was basically calling:

	perf_session__delete(ERR_PTR(-1))

Resulting in:

  (gdb) run lock contention
  Starting program: /root/bin/perf lock contention
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib64/libthread_db.so.1".
  failed to open perf.data: No such file or directory  (try 'perf record' first)
  Initializing perf session failed

  Program received signal SIGSEGV, Segmentation fault.
  0x00000000005e7515 in auxtrace__free (session=0xffffffffffffffff) at util/auxtrace.c:2858
  2858		if (!session->auxtrace)
  (gdb) p session
  $1 = (struct perf_session *) 0xffffffffffffffff
  (gdb) bt
  #0  0x00000000005e7515 in auxtrace__free (session=0xffffffffffffffff) at util/auxtrace.c:2858
  #1  0x000000000057bb4d in perf_session__delete (session=0xffffffffffffffff) at util/session.c:300
  #2  0x000000000047c421 in __cmd_contention (argc=0, argv=0x7fffffffe200) at builtin-lock.c:2161
  #3  0x000000000047dc95 in cmd_lock (argc=0, argv=0x7fffffffe200) at builtin-lock.c:2604
  #4  0x0000000000501466 in run_builtin (p=0xe597a8 <commands+552>, argc=2, argv=0x7fffffffe200) at perf.c:322
  #5  0x00000000005016d5 in handle_internal_command (argc=2, argv=0x7fffffffe200) at perf.c:375
  #6  0x0000000000501824 in run_argv (argcp=0x7fffffffe02c, argv=0x7fffffffe020) at perf.c:419
  #7  0x0000000000501b11 in main (argc=2, argv=0x7fffffffe200) at perf.c:535
  (gdb)

So just set it to NULL after using PTR_ERR(session) to decode the error
as perf_session__delete(NULL) is supported.

Fixes: 6ef81c55a2b6584c ("perf session: Return error code for perf_session__new() function on failure")
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jeremie Galarneau <jeremie.galarneau@...icios.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Kate Stewart <kstewart@...uxfoundation.org>
Cc: Mamatha Inamdar <mamatha4@...ux.vnet.ibm.com>
Cc: Mukesh Ojha <mojha@...eaurora.org>
Cc: Nageswara R Sastry <rnsastry@...ux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc: Shawn Landden <shawn@....icu>
Cc: Song Liu <songliubraving@...com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Tzvetomir Stoyanov <tstoyanov@...are.com>
Link: https://lore.kernel.org/lkml/
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-top.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 1baa2acb3cedd989..ea8c7eca5eeedd76 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1805,6 +1805,7 @@ int cmd_top(int argc, const char **argv)
 	top.session = perf_session__new(NULL, NULL);
 	if (IS_ERR(top.session)) {
 		status = PTR_ERR(top.session);
+		top.session = NULL;
 		goto out_delete_evlist;
 	}
 
-- 
2.37.1