[PATCH RESEND v4] perf record: Fix segfault with --overwrite and --max-size

[PATCH RESEND v4] perf record: Fix segfault with --overwrite and --max-size

[Yang Jihong]

When --overwrite and --max-size options of perf record are used together,
a segmentation fault occurs. The following is an example:

  # perf record -e sched:sched* --overwrite --max-size 1K -a -- sleep 1
  [ perf record: Woken up 1 times to write data ]
  perf: Segmentation fault
  Obtained 12 stack frames.
  ./perf/perf(+0x197673) [0x55f99710b673]
  /lib/x86_64-linux-gnu/libc.so.6(+0x3ef0f) [0x7fa45f3cff0f]
  ./perf/perf(+0x8eb40) [0x55f997002b40]
  ./perf/perf(+0x1f6882) [0x55f99716a882]
  ./perf/perf(+0x794c2) [0x55f996fed4c2]
  ./perf/perf(+0x7b7c7) [0x55f996fef7c7]
  ./perf/perf(+0x9074b) [0x55f99700474b]
  ./perf/perf(+0x12e23c) [0x55f9970a223c]
  ./perf/perf(+0x12e54a) [0x55f9970a254a]
  ./perf/perf(+0x7db60) [0x55f996ff1b60]
  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe6) [0x7fa45f3b2c86]
  ./perf/perf(+0x7dfe9) [0x55f996ff1fe9]
  Segmentation fault (core dumped)

backtrace of the core file is as follows:

  (gdb) bt
  #0  record__bytes_written (rec=0x55f99755a200 <record>) at builtin-record.c:234
  #1  record__output_max_size_exceeded (rec=0x55f99755a200 <record>) at builtin-record.c:242
  #2  record__write (map=0x0, size=12816, bf=0x55f9978da2e0, rec=0x55f99755a200 <record>) at builtin-record.c:263
  #3  process_synthesized_event (tool=tool@entry=0x55f99755a200 <record>, event=event@entry=0x55f9978da2e0, sample=sample@entry=0x0, machine=machine@entry=0x55f997893658) at builtin-record.c:618
  #4  0x000055f99716a883 in __perf_event__synthesize_id_index (tool=tool@entry=0x55f99755a200 <record>, process=process@entry=0x55f997002aa0 <process_synthesized_event>, evlist=0x55f9978928b0, machine=machine@entry=0x55f997893658,
      from=from@entry=0) at util/synthetic-events.c:1895
  #5  0x000055f99716a91f in perf_event__synthesize_id_index (tool=tool@entry=0x55f99755a200 <record>, process=process@entry=0x55f997002aa0 <process_synthesized_event>, evlist=<optimized out>, machine=machine@entry=0x55f997893658)
      at util/synthetic-events.c:1905
  #6  0x000055f996fed4c3 in record__synthesize (tail=tail@entry=true, rec=0x55f99755a200 <record>) at builtin-record.c:1997
  #7  0x000055f996fef7c8 in __cmd_record (argc=argc@entry=2, argv=argv@entry=0x7ffc67551260, rec=0x55f99755a200 <record>) at builtin-record.c:2802
  #8  0x000055f99700474c in cmd_record (argc=<optimized out>, argv=0x7ffc67551260) at builtin-record.c:4258
  #9  0x000055f9970a223d in run_builtin (p=0x55f997564d88 <commands+264>, argc=10, argv=0x7ffc67551260) at perf.c:330
  #10 0x000055f9970a254b in handle_internal_command (argc=10, argv=0x7ffc67551260) at perf.c:384
  #11 0x000055f996ff1b61 in run_argv (argcp=<synthetic pointer>, argv=<synthetic pointer>) at perf.c:428
  #12 main (argc=<optimized out>, argv=0x7ffc67551260) at perf.c:562

The reason is that record__bytes_written accesses the freed memory rec->thread_data,
The process is as follows:
  __cmd_record
    -> record__free_thread_data
      -> zfree(&rec->thread_data)         // free rec->thread_data
    -> record__synthesize
      -> perf_event__synthesize_id_index
        -> process_synthesized_event
          -> record__write
            -> record__bytes_written      // access rec->thread_data

We add a member variable "thread_bytes_written" in the struct "record"
to save the data size written by the threads.

Fixes: 6d57581659f7 ("perf record: Add support for limit perf output file size")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
---

Changes since v3:
 - Add Namhyung Kim Acked-by
   (I don't know whether the problem is caused by my email address, Send again)

Changes since v2:
 - Save data size written by threads to calculate the correct total data size.
 - Update commit message.

Changes since v1:
 - Add variable check in record__bytes_written for code hardening.
 - Save bytes_written separately to reduce one calculation.
 - Remove rec->opts.tail_synthesize check.

 tools/perf/builtin-record.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 29dcd454b8e2..8374117e66f6 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -154,6 +154,7 @@ struct record {
 	struct perf_tool	tool;
 	struct record_opts	opts;
 	u64			bytes_written;
+	u64			thread_bytes_written;
 	struct perf_data	data;
 	struct auxtrace_record	*itr;
 	struct evlist	*evlist;
@@ -226,14 +227,7 @@ static bool switch_output_time(struct record *rec)
 
 static u64 record__bytes_written(struct record *rec)
 {
-	int t;
-	u64 bytes_written = rec->bytes_written;
-	struct record_thread *thread_data = rec->thread_data;
-
-	for (t = 0; t < rec->nr_threads; t++)
-		bytes_written += thread_data[t].bytes_written;
-
-	return bytes_written;
+	return rec->bytes_written + rec->thread_bytes_written;
 }
 
 static bool record__output_max_size_exceeded(struct record *rec)
@@ -255,10 +249,12 @@ static int record__write(struct record *rec, struct mmap *map __maybe_unused,
 		return -1;
 	}
 
-	if (map && map->file)
+	if (map && map->file) {
 		thread->bytes_written += size;
-	else
+		rec->thread_bytes_written += size;
+	} else {
 		rec->bytes_written += size;
+	}
 
 	if (record__output_max_size_exceeded(rec) && !done) {
 		fprintf(stderr, "[ perf record: perf size limit reached (%" PRIu64 " KB),"
-- 
2.30.GIT

Re: [PATCH RESEND v4] perf record: Fix segfault with --overwrite and --max-size

[Arnaldo Carvalho de Melo]

Em Wed, Feb 15, 2023 at 12:23:24PM +0000, Yang Jihong escreveu:
> When --overwrite and --max-size options of perf record are used together,
> a segmentation fault occurs. The following is an example:
<SNIP>
> We add a member variable "thread_bytes_written" in the struct "record"
> to save the data size written by the threads.
> 
> Fixes: 6d57581659f7 ("perf record: Add support for limit perf output file size")
> Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
> Acked-by: Namhyung Kim <namhyung@kernel.org>
> ---
> 
> Changes since v3:
>  - Add Namhyung Kim Acked-by
>    (I don't know whether the problem is caused by my email address, Send again)

Thanks, applied.

- Arnaldo

 
> Changes since v2:
>  - Save data size written by threads to calculate the correct total data size.
>  - Update commit message.
> 
> Changes since v1:
>  - Add variable check in record__bytes_written for code hardening.
>  - Save bytes_written separately to reduce one calculation.
>  - Remove rec->opts.tail_synthesize check.
> 
>  tools/perf/builtin-record.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 29dcd454b8e2..8374117e66f6 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -154,6 +154,7 @@ struct record {
>  	struct perf_tool	tool;
>  	struct record_opts	opts;
>  	u64			bytes_written;
> +	u64			thread_bytes_written;
>  	struct perf_data	data;
>  	struct auxtrace_record	*itr;
>  	struct evlist	*evlist;
> @@ -226,14 +227,7 @@ static bool switch_output_time(struct record *rec)
>  
>  static u64 record__bytes_written(struct record *rec)
>  {
> -	int t;
> -	u64 bytes_written = rec->bytes_written;
> -	struct record_thread *thread_data = rec->thread_data;
> -
> -	for (t = 0; t < rec->nr_threads; t++)
> -		bytes_written += thread_data[t].bytes_written;
> -
> -	return bytes_written;
> +	return rec->bytes_written + rec->thread_bytes_written;
>  }
>  
>  static bool record__output_max_size_exceeded(struct record *rec)
> @@ -255,10 +249,12 @@ static int record__write(struct record *rec, struct mmap *map __maybe_unused,
>  		return -1;
>  	}
>  
> -	if (map && map->file)
> +	if (map && map->file) {
>  		thread->bytes_written += size;
> -	else
> +		rec->thread_bytes_written += size;
> +	} else {
>  		rec->bytes_written += size;
> +	}
>  
>  	if (record__output_max_size_exceeded(rec) && !done) {
>  		fprintf(stderr, "[ perf record: perf size limit reached (%" PRIu64 " KB),"
> -- 
> 2.30.GIT
> 

-- 

- Arnaldo