[PATCH 0/3] perf record: Fix segfault with '--timestamp-filename' option and pipe mode

[PATCH 0/3] perf record: Fix segfault with '--timestamp-filename' option and pipe mode

[Yang Jihong]

When perf record uses '--timestamp-filename' option and pipe mode,
will occur segfault:

  # perf record --timestamp-filename -o- true 1>/dev/null
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Dump -.2024011813361681 ]
  perf: Segmentation fault
  Segmentation fault (core dumped)

Debug the core file by using the gdb:

  # gdb perf core.3706841
  <SNIP>
  [New LWP 3706841]
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  Core was generated by `perf record --timestamp-filename -o- true'.
  Program terminated with signal SIGSEGV, Segmentation fault.
  #0  evsel__free_stat_priv (evsel=0x555ea56197af) at util/stat.c:145
  145             struct perf_stat_evsel *ps = evsel->stats;
  (gdb) bt
  #0  evsel__free_stat_priv (evsel=0x555ea56197af) at util/stat.c:145
  #1  evlist__free_stats (evlist=evlist@entry=0x555bf0dad1b0) at util/stat.c:215
  #2  0x0000555befd425e8 in evlist__delete (evlist=0x555bf0dad1b0) at util/evlist.c:175
  #3  0x0000555befd42785 in evlist__delete (evlist=<optimized out>) at util/evlist.c:181
  #4  0x0000555befc7f547 in cmd_record (argc=<optimized out>, argv=<optimized out>) at builtin-record.c:4252
  #5  0x0000555befd27700 in run_builtin (p=p@entry=0x555bf05acf88 <commands+264>, argc=argc@entry=4, argv=argv@entry=0x7ffc2696a920) at perf.c:349
  #6  0x0000555befc68751 in handle_internal_command (argv=0x7ffc2696a920, argc=4) at perf.c:402
  #7  run_argv (argv=<synthetic pointer>, argcp=<synthetic pointer>) at perf.c:446
  #8  main (argc=4, argv=0x7ffc2696a920) at perf.c:562

It is found that the memory of the evsel is modified.
The reason is that perf_data__switch() not initialized 'new_filename',
as a result, it uses the on-stack variable. It happens that the evsel
address is stored here. 'new_filename' is freed later when uses
'--timestamp-filename' option. Therefore, segfault occurs in the evsel_delete().


1. patch1 fixes this problem.
2. patch2 to optimize the process, check conflict between
   '--timestamp-filename' option and the pipe mode before recording to
   avoid switch perf data.
3. patch3 fixes the code style problem by the way.


Yang Jihong (3):
  perf record: Fix possible incorrect free in record__switch_output()
  perf record: Check conflict between '--timestamp-filename' option and
    pipe mode before recording
  perf data: Minor code style alignment cleanup

 tools/perf/builtin-record.c | 14 ++++++++++----
 tools/perf/util/data.c      | 10 ++++------
 tools/perf/util/data.h      |  6 +++---
 3 files changed, 17 insertions(+), 13 deletions(-)

-- 
2.34.1

[PATCH 1/3] perf record: Fix possible incorrect free in record__switch_output()

[Yang Jihong]

perf_data__switch() may not assign a legal value to 'new_filename'.
In this case, 'new_filename' uses the on-stack value, which may cause a
incorrect free and unexpected result.

Fixes: 03724b2e9c45 ("perf record: Allow to limit number of reported perf.data files")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
---
 tools/perf/builtin-record.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 91e6828c38cc..fb8d4067b76c 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1830,8 +1830,8 @@ static int
 record__switch_output(struct record *rec, bool at_exit)
 {
 	struct perf_data *data = &rec->data;
+	char *new_filename = NULL;
 	int fd, err;
-	char *new_filename;
 
 	/* Same Size:      "2015122520103046"*/
 	char timestamp[] = "InvalidTimestamp";
-- 
2.34.1

[PATCH 2/3] perf record: Check conflict between '--timestamp-filename' option and pipe mode before recording

[Yang Jihong]

In pipe mode, no need to switch perf data output, therefore,
'--timestamp-filename' option should not take effect.
Check the conflict before recording and output WARNING.
In this case, the check pipe mode in perf_data__switch() can be removed.

Before:

  # perf record --timestamp-filename -o- perf test -w noploop | perf report -i- --percent-limit=1
  # To display the perf.data header info, please use --header/--header-only options.
  #
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Dump -.2024011812110182 ]
  #
  # Total Lost Samples: 0
  #
  # Samples: 4K of event 'cycles:P'
  # Event count (approx.): 2176784359
  #
  # Overhead  Command  Shared Object         Symbol
  # ........  .......  ....................  ......................................
  #
      97.83%  perf     perf                  [.] noploop

  #
  # (Tip: Print event counts in CSV format with: perf stat -x,)
  #

After:

  # perf record --timestamp-filename -o- perf test -w noploop | perf report -i- --percent-limit=1
  WARNING: --timestamp-filename option is not available in pipe mode.
  # To display the perf.data header info, please use --header/--header-only options.
  #
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.000 MB - ]
  #
  # Total Lost Samples: 0
  #
  # Samples: 4K of event 'cycles:P'
  # Event count (approx.): 2185575421
  #
  # Overhead  Command  Shared Object          Symbol
  # ........  .......  .....................  .............................................
  #
      97.75%  perf     perf                   [.] noploop

  #
  # (Tip: Profiling branch (mis)predictions with: perf record -b / perf report)
  #

Fixes: ecfd7a9c044e ("perf record: Add '--timestamp-filename' option to append timestamp to output file name")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
---
 tools/perf/builtin-record.c | 5 +++++
 tools/perf/util/data.c      | 2 --
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index fb8d4067b76c..5e3ea5cf1429 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -2472,6 +2472,11 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	if (data->is_pipe && rec->evlist->core.nr_entries == 1)
 		rec->opts.sample_id = true;
 
+	if (rec->timestamp_filename && perf_data__is_pipe(data)) {
+		rec->timestamp_filename = false;
+		pr_warning("WARNING: --timestamp-filename option is not available in pipe mode.\n");
+	}
+
 	evlist__uniquify_name(rec->evlist);
 
 	/* Debug message used by test scripts */
diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
index c29d8a382b19..550675ce0b78 100644
--- a/tools/perf/util/data.c
+++ b/tools/perf/util/data.c
@@ -430,8 +430,6 @@ int perf_data__switch(struct perf_data *data,
 {
 	int ret;
 
-	if (check_pipe(data))
-		return -EINVAL;
 	if (perf_data__is_read(data))
 		return -EINVAL;
 
-- 
2.34.1

[PATCH 3/3] perf data: Minor code style alignment cleanup

[Yang Jihong]

Minor code style alignment cleanup for perf_data__switch() and
perf_data__write().

No functional change.

Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
---
 tools/perf/builtin-record.c | 7 ++++---
 tools/perf/util/data.c      | 8 ++++----
 tools/perf/util/data.h      | 6 +++---
 3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 5e3ea5cf1429..0b6f29fa0064 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1853,16 +1853,17 @@ record__switch_output(struct record *rec, bool at_exit)
 	}
 
 	fd = perf_data__switch(data, timestamp,
-				    rec->session->header.data_offset,
-				    at_exit, &new_filename);
+			       rec->session->header.data_offset,
+			       at_exit, &new_filename);
 	if (fd >= 0 && !at_exit) {
 		rec->bytes_written = 0;
 		rec->session->header.data_size = 0;
 	}
 
-	if (!quiet)
+	if (!quiet) {
 		fprintf(stderr, "[ perf record: Dump %s.%s ]\n",
 			data->path, timestamp);
+	}
 
 	if (rec->switch_output.num_files) {
 		int n = rec->switch_output.cur_file + 1;
diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
index 550675ce0b78..08c4bfbd817f 100644
--- a/tools/perf/util/data.c
+++ b/tools/perf/util/data.c
@@ -413,7 +413,7 @@ ssize_t perf_data_file__write(struct perf_data_file *file,
 }
 
 ssize_t perf_data__write(struct perf_data *data,
-			      void *buf, size_t size)
+			 void *buf, size_t size)
 {
 	if (data->use_stdio) {
 		if (fwrite(buf, size, 1, data->file.fptr) == 1)
@@ -424,9 +424,9 @@ ssize_t perf_data__write(struct perf_data *data,
 }
 
 int perf_data__switch(struct perf_data *data,
-			   const char *postfix,
-			   size_t pos, bool at_exit,
-			   char **new_filepath)
+		      const char *postfix,
+		      size_t pos, bool at_exit,
+		      char **new_filepath)
 {
 	int ret;
 
diff --git a/tools/perf/util/data.h b/tools/perf/util/data.h
index effcc195d7e9..110f3ebde30f 100644
--- a/tools/perf/util/data.h
+++ b/tools/perf/util/data.h
@@ -80,7 +80,7 @@ int perf_data__open(struct perf_data *data);
 void perf_data__close(struct perf_data *data);
 ssize_t perf_data__read(struct perf_data *data, void *buf, size_t size);
 ssize_t perf_data__write(struct perf_data *data,
-			      void *buf, size_t size);
+			 void *buf, size_t size);
 ssize_t perf_data_file__write(struct perf_data_file *file,
 			      void *buf, size_t size);
 /*
@@ -91,8 +91,8 @@ ssize_t perf_data_file__write(struct perf_data_file *file,
  * Return value is fd of new output.
  */
 int perf_data__switch(struct perf_data *data,
-			   const char *postfix,
-			   size_t pos, bool at_exit, char **new_filepath);
+		      const char *postfix,
+		      size_t pos, bool at_exit, char **new_filepath);
 
 int perf_data__create_dir(struct perf_data *data, int nr);
 int perf_data__open_dir(struct perf_data *data);
-- 
2.34.1

Re: [PATCH 0/3] perf record: Fix segfault with '--timestamp-filename' option and pipe mode

[Namhyung Kim]

Hello,

On Thu, Jan 18, 2024 at 8:07 PM Yang Jihong <yangjihong1@huawei.com> wrote:
>
> When perf record uses '--timestamp-filename' option and pipe mode,
> will occur segfault:
>
>   # perf record --timestamp-filename -o- true 1>/dev/null
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Dump -.2024011813361681 ]
>   perf: Segmentation fault
>   Segmentation fault (core dumped)
>
> Debug the core file by using the gdb:
>
>   # gdb perf core.3706841
>   <SNIP>
>   [New LWP 3706841]
>   [Thread debugging using libthread_db enabled]
>   Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
>   Core was generated by `perf record --timestamp-filename -o- true'.
>   Program terminated with signal SIGSEGV, Segmentation fault.
>   #0  evsel__free_stat_priv (evsel=0x555ea56197af) at util/stat.c:145
>   145             struct perf_stat_evsel *ps = evsel->stats;
>   (gdb) bt
>   #0  evsel__free_stat_priv (evsel=0x555ea56197af) at util/stat.c:145
>   #1  evlist__free_stats (evlist=evlist@entry=0x555bf0dad1b0) at util/stat.c:215
>   #2  0x0000555befd425e8 in evlist__delete (evlist=0x555bf0dad1b0) at util/evlist.c:175
>   #3  0x0000555befd42785 in evlist__delete (evlist=<optimized out>) at util/evlist.c:181
>   #4  0x0000555befc7f547 in cmd_record (argc=<optimized out>, argv=<optimized out>) at builtin-record.c:4252
>   #5  0x0000555befd27700 in run_builtin (p=p@entry=0x555bf05acf88 <commands+264>, argc=argc@entry=4, argv=argv@entry=0x7ffc2696a920) at perf.c:349
>   #6  0x0000555befc68751 in handle_internal_command (argv=0x7ffc2696a920, argc=4) at perf.c:402
>   #7  run_argv (argv=<synthetic pointer>, argcp=<synthetic pointer>) at perf.c:446
>   #8  main (argc=4, argv=0x7ffc2696a920) at perf.c:562
>
> It is found that the memory of the evsel is modified.
> The reason is that perf_data__switch() not initialized 'new_filename',
> as a result, it uses the on-stack variable. It happens that the evsel
> address is stored here. 'new_filename' is freed later when uses
> '--timestamp-filename' option. Therefore, segfault occurs in the evsel_delete().
>
>
> 1. patch1 fixes this problem.
> 2. patch2 to optimize the process, check conflict between
>    '--timestamp-filename' option and the pipe mode before recording to
>    avoid switch perf data.
> 3. patch3 fixes the code style problem by the way.
>
>
> Yang Jihong (3):
>   perf record: Fix possible incorrect free in record__switch_output()
>   perf record: Check conflict between '--timestamp-filename' option and
>     pipe mode before recording
>   perf data: Minor code style alignment cleanup

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

>
>  tools/perf/builtin-record.c | 14 ++++++++++----
>  tools/perf/util/data.c      | 10 ++++------
>  tools/perf/util/data.h      |  6 +++---
>  3 files changed, 17 insertions(+), 13 deletions(-)
>
> --
> 2.34.1
>

Re: [PATCH 0/3] perf record: Fix segfault with '--timestamp-filename' option and pipe mode

[Namhyung Kim]

On Fri, 19 Jan 2024 04:03:01 +0000, Yang Jihong wrote:
> When perf record uses '--timestamp-filename' option and pipe mode,
> will occur segfault:
> 
>   # perf record --timestamp-filename -o- true 1>/dev/null
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Dump -.2024011813361681 ]
>   perf: Segmentation fault
>   Segmentation fault (core dumped)
> 
> [...]

Applied to perf-tools-next, thanks!

Namhyung