[PATCH] perf trace: propagate evsel__set_filter() error in trace__expand_filter()

[PATCH] perf trace: propagate evsel__set_filter() error in trace__expand_filter()

[Gu Bin]

At the end of trace__expand_filter(), the return value of
evsel__set_filter() is ignored. When the strdup() inside fails with
-ENOMEM, the function returns 0 anyway, leaving evsel->filter holding
the unexpanded filter, which still contains the symbolic constants the
loop meant to resolve. The failure then surfaces later and indirectly:
evlist__apply_filters() passes the unexpanded string to the tracepoint
filter parser, which rejects the symbolic name, so perf trace fails to
start with a filter syntax error whose real cause is the missed
allocation.

Propagate the error so the -ENOMEM is reported at the source and the
caller fails immediately.

Fixes: 90df0249c2ea ("perf trace: Expand strings in filters to integers")
Signed-off-by: Gu Bin <gubin@cmss.chinamobile.com>
---
 tools/perf/builtin-trace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Found by the sashiko review of the fix to the asprintf() failure path
in the same function ([PATCH] perf trace: guard free(new_filter) to
avoid double-free on OOM), which flagged the unchecked return value of
evsel__set_filter() as a related pre-existing issue:

  https://sashiko.dev/#/bug/linux-cbf4bb01-a981-47dc-b440-68e5c9c3e81c

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 4094141461f91..ce1a7352ea9dd 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -4704,9 +4704,13 @@ static int trace__expand_filter(struct trace *trace, struct evsel *evsel)
 	}
 
 	if (new_filter != evsel->filter) {
+		int err;
+
 		pr_debug("New filter for %s: %s\n", evsel->name, new_filter);
-		evsel__set_filter(evsel, new_filter);
+		err = evsel__set_filter(evsel, new_filter);
 		free(new_filter);
+		if (err)
+			return err;
 	}
 
 	return 0;
-- 
2.50.1.windows.1

Re: [PATCH] perf trace: propagate evsel__set_filter() error in trace__expand_filter()

[sashiko-bot]

> At the end of trace__expand_filter(), the return value of
> evsel__set_filter() is ignored. When the strdup() inside fails with
> -ENOMEM, the function returns 0 anyway, leaving evsel->filter holding
> the unexpanded filter, which still contains the symbolic constants the
> loop meant to resolve. The failure then surfaces later and indirectly:
> evlist__apply_filters() passes the unexpanded string to the tracepoint
> filter parser, which rejects the symbolic name, so perf trace fails to
> start with a filter syntax error whose real cause is the missed
> allocation.
> 
> Propagate the error so the -ENOMEM is reported at the source and the
> caller fails immediately.
> 
> Fixes: 90df0249c2ea ("perf trace: Expand strings in filters to integers")
> Signed-off-by: Gu Bin <gubin@cmss.chinamobile.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112080924.2082-1-gubin@cmss.chinamobile.com?part=1