linux-kernel - [PATCH v2 2/2] perf probe: Fix libdw memory leak

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Message-Id: <20241016235622.52166-3-irogers@google.com>
Date: Wed, 16 Oct 2024 16:56:22 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Kajol Jain <kjain@...ux.ibm.com>, 
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, "Steinar H. Gunderson" <sesse@...gle.com>, 
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Alexander Lobakin <aleksander.lobakin@...el.com>, 
	"David S. Miller" <davem@...emloft.net>, Hemant Kumar <hemant@...ux.vnet.ibm.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] perf probe: Fix libdw memory leak

Add missing dwarf_cfi_end to free memory associated with probe_finder
cfi_eh which is allocated and owned via a call to
dwarf_getcfi_elf. Confusingly cfi_dbg shouldn't be freed as its memory
is owned by the passed in debuginfo struct. Add comments to highlight
this.

This addresses leak sanitizer issues seen in:
tools/perf/tests/shell/test_uprobe_from_different_cu.sh

Fixes: 270bde1e76f4 ("perf probe: Search both .eh_frame and .debug_frame sections for probe location")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/probe-finder.c | 4 ++++
 tools/perf/util/probe-finder.h | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 630e16c54ed5..d6b902899940 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1379,6 +1379,10 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
 	if (ret >= 0 && tf.pf.skip_empty_arg)
 		ret = fill_empty_trace_arg(pev, tf.tevs, tf.ntevs);
 
+#if _ELFUTILS_PREREQ(0, 142)
+	dwarf_cfi_end(tf.pf.cfi_eh);
+#endif
+
 	if (ret < 0 || tf.ntevs == 0) {
 		for (i = 0; i < tf.ntevs; i++)
 			clear_probe_trace_event(&tf.tevs[i]);
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index 3add5ff516e1..724db829b49e 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -64,9 +64,9 @@ struct probe_finder {
 
 	/* For variable searching */
 #if _ELFUTILS_PREREQ(0, 142)
-	/* Call Frame Information from .eh_frame */
+	/* Call Frame Information from .eh_frame. Owned by this struct. */
 	Dwarf_CFI		*cfi_eh;
-	/* Call Frame Information from .debug_frame */
+	/* Call Frame Information from .debug_frame. Not owned. */
 	Dwarf_CFI		*cfi_dbg;
 #endif
 	Dwarf_Op		*fb_ops;	/* Frame base attribute */
-- 
2.47.0.105.g07ac214952-goog