[PATCH 6.11 525/817] perf trace: avoid garbage when not printing a trace events arguments

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6.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Peterson <benjamin@xxxxxxxxxxx>

[ Upstream commit 5fb8e56542a3cf469fdf25d77f50e21cbff3ae7e ]

trace__fprintf_tp_fields may not print any tracepoint arguments. E.g., if the
argument values are all zero. Previously, this would result in a totally
uninitialized buffer being passed to fprintf, which could lead to garbage on the
console. Fix the problem by passing the number of initialized bytes fprintf.

Fixes: f11b2803bb88 ("perf trace: Allow choosing how to augment the tracepoint arguments")
Signed-off-by: Benjamin Peterson <benjamin@xxxxxxxxxxx>
Tested-by: Howard Chu <howardchu95@xxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241103204816.7834-1-benjamin@xxxxxxxxxxx
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/perf/builtin-trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 19db23f78b199..5298118ffb15f 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2802,7 +2802,7 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct evsel *evsel,
 		printed += syscall_arg_fmt__scnprintf_val(arg, bf + printed, size - printed, &syscall_arg, val);
 	}
 
-	return printed + fprintf(trace->output, "%s", bf);
+	return printed + fprintf(trace->output, "%.*s", (int)printed, bf);
 }
 
 static int trace__event_handler(struct trace *trace, struct evsel *evsel,
-- 
2.43.0







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