Re: [PATCH] perf data convert json: Fix trace_seq memory leak in process_sample_event()

[Tanushree Shah]

Hello Arnaldo

Thanks for checking the patch. I cannot see this patch applied on 
perf-tools-next yet.

https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/log/?h=perf-tools-next

Thanks.

On 05/06/26 02:59, Arnaldo Carvalho de Melo wrote:
On Thu, Jun 04, 2026 at 12:25:19PM +0530, Tanushree Shah wrote:
Unlike the in-kernel trace_seq which uses a statically allocated buffer,
the userspace traceevent library's trace_seq uses a dynamically allocated
one. Therefore, every trace_seq_init() call must be paired with a
trace_seq_destroy(), otherwise it produces a memory leak.

In process_sample_event(), a trace_seq is initialized for each field when
formatting tracepoint raw_data, but the matching trace_seq_destroy() is
never called, leaking memory for every field of every sample processed.

Add the missing trace_seq_destroy() after using the trace_seq buffer to
properly free the allocated memory.

Detected with Valgrind on a perf.data file with 2,729 tracepoint samples:
   Before: definitely lost: 55,537,664 bytes in 13,559 blocks
   After:  definitely lost: 0 bytes in 0 blocks

Thanks, applied to perf-tools-next, for v7.2.

- Arnaldo
  
Fixes: 9d895e468429 ("perf data: Add tracepoint fields when converting to JSON")
Signed-off-by: Tanushree Shah <ts...@linux.ibm.com>
---
  tools/perf/util/data-convert-json.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/data-convert-json.c 
b/tools/perf/util/data-convert-json.c
index d526c91312ed..6dd9349ab10f 100644
--- a/tools/perf/util/data-convert-json.c
+++ b/tools/perf/util/data-convert-json.c
@@ -257,6 +257,7 @@ static int process_sample_event(const struct perf_tool 
*tool,
                                trace_seq_init(&s);
                                tep_print_field(&s, sample->raw_data, 
fields[i]);
                                output_json_key_string(out, true, 3, 
fields[i]->name, s.buffer);
+                               trace_seq_destroy(&s);
  
  				i++;
                        }
--
2.47.3