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Date:   Wed,  3 Feb 2021 10:25:07 +0800
From:   Jianlin Lv <Jianlin.Lv@....com>
To:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org, mhiramat@...nel.org,
        srikar@...ux.vnet.ibm.com, adrian.hunter@...el.com
Cc:     Jianlin.Lv@....com, linux-kernel@...r.kernel.org
Subject: [PATCH] perf probe: Added protection to avoid endless loop

if dwarf_offdie() return NULL, the continue statement forces the next
iteration of the loop without update variable off. It will cause an
endless loop in the process of traversing the compilation unit.
So added exception protection for loop CUs.

Signed-off-by: Jianlin Lv <Jianlin.Lv@....com>
---
 tools/perf/util/probe-finder.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 76dd349aa48d..887bffb1cc58 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1156,7 +1156,7 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
 	Dwarf_Die *diep;
 	int ret = 0;
 
-	off = 0;
+	noff = 0;
 	pf->lcache = intlist__new(NULL);
 	if (!pf->lcache)
 		return -ENOMEM;
@@ -1184,7 +1184,7 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
 	}
 
 	/* Loop on CUs (Compilation Unit) */
-	while (!dwarf_nextcu(dbg->dbg, off, &noff, &cuhl, NULL, NULL, NULL)) {
+	while (!dwarf_nextcu(dbg->dbg, off = noff, &noff, &cuhl, NULL, NULL, NULL)) {
 		/* Get the DIE(Debugging Information Entry) of this CU */
 		diep = dwarf_offdie(dbg->dbg, off + cuhl, &pf->cu_die);
 		if (!diep)
@@ -1208,7 +1208,6 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
 			if (ret < 0)
 				break;
 		}
-		off = noff;
 	}
 
 found:
@@ -1919,7 +1918,7 @@ int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr)
 {
 	struct line_finder lf = {.lr = lr, .found = 0};
 	int ret = 0;
-	Dwarf_Off off = 0, noff;
+	Dwarf_Off off = 0, noff = 0;
 	size_t cuhl;
 	Dwarf_Die *diep;
 	const char *comp_dir;
@@ -1943,6 +1942,7 @@ int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr)
 
 	/* Loop on CUs (Compilation Unit) */
 	while (!lf.found && ret >= 0) {
+		off = noff;
 		if (dwarf_nextcu(dbg->dbg, off, &noff, &cuhl,
 				 NULL, NULL, NULL) != 0)
 			break;
@@ -1967,7 +1967,6 @@ int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr)
 				ret = find_line_range_by_line(NULL, &lf);
 			}
 		}
-		off = noff;
 	}
 
 found:
-- 
2.25.1

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