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Date:   Tue, 24 Oct 2023 15:23:05 -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>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Nick Terrell <terrelln@...com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, Leo Yan <leo.yan@...aro.org>,
        Song Liu <song@...nel.org>,
        Sandipan Das <sandipan.das@....com>,
        James Clark <james.clark@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Liam Howlett <liam.howlett@...cle.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Ravi Bangoria <ravi.bangoria@....com>,
        German Gomez <german.gomez@....com>,
        Changbin Du <changbin.du@...wei.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        liuwenyu <liuwenyu7@...wei.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: [PATCH v3 02/50] perf machine: Avoid out of bounds LBR memory read

Running perf top with address sanitizer and "--call-graph=lbr" fails
due to reading sample 0 when no samples exist. Add a guard to prevent
this.

Fixes: e2b23483eb1d ("perf machine: Factor out lbr_callchain_add_lbr_ip()")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/machine.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index addfae2f63ef..e0e2c4a943e4 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -2622,16 +2622,18 @@ static int lbr_callchain_add_lbr_ip(struct thread *thread,
 		save_lbr_cursor_node(thread, cursor, i);
 	}
 
-	/* Add LBR ip from first entries.to */
-	ip = entries[0].to;
-	flags = &entries[0].flags;
-	*branch_from = entries[0].from;
-	err = add_callchain_ip(thread, cursor, parent,
-			       root_al, &cpumode, ip,
-			       true, flags, NULL,
-			       *branch_from);
-	if (err)
-		return err;
+	if (lbr_nr > 0) {
+		/* Add LBR ip from first entries.to */
+		ip = entries[0].to;
+		flags = &entries[0].flags;
+		*branch_from = entries[0].from;
+		err = add_callchain_ip(thread, cursor, parent,
+				root_al, &cpumode, ip,
+				true, flags, NULL,
+				*branch_from);
+		if (err)
+			return err;
+	}
 
 	return 0;
 }
-- 
2.42.0.758.gaed0368e0e-goog

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