[PATCH] perf report: don't crash on invalid maps in `-g srcline` mode

[Milian Wolff]

I just hit a segfault when doing `perf report -g srcline`.
Valgrind pointed me at this code as the culprit:

==8359== Invalid read of size 8
==8359==    at 0x3096D9: map__rip_2objdump (map.c:430)
==8359==    by 0x2FC1A3: match_chain_srcline (callchain.c:645)
==8359==    by 0x2FC1A3: match_chain (callchain.c:700)
==8359==    by 0x2FC1A3: append_chain (callchain.c:895)
==8359==    by 0x2FC1A3: append_chain_children (callchain.c:846)
==8359==    by 0x2FF719: callchain_append (callchain.c:944)
==8359==    by 0x2FF719: hist_entry__append_callchain (callchain.c:1058)
==8359==    by 0x32FA06: iter_add_single_cumulative_entry (hist.c:908)
==8359==    by 0x33195C: hist_entry_iter__add (hist.c:1050)
==8359==    by 0x258F65: process_sample_event (builtin-report.c:204)
==8359==    by 0x30D60C: perf_session__deliver_event (session.c:1310)
==8359==    by 0x30D60C: ordered_events__deliver_event (session.c:119)
==8359==    by 0x310D12: __ordered_events__flush (ordered-events.c:210)
==8359==    by 0x310D12: ordered_events__flush.part.3 (ordered-events.c:277)
==8359==    by 0x30DD3C: perf_session__process_user_event (session.c:1349)
==8359==    by 0x30DD3C: perf_session__process_event (session.c:1475)
==8359==    by 0x30FC3C: __perf_session__process_events (session.c:1867)
==8359==    by 0x30FC3C: perf_session__process_events (session.c:1921)
==8359==    by 0x25A985: __cmd_report (builtin-report.c:575)
==8359==    by 0x25A985: cmd_report (builtin-report.c:1054)
==8359==    by 0x2B9A80: run_builtin (perf.c:296)
==8359==  Address 0x70 is not stack'd, malloc'd or (recently) free'd

This patch fixes the issue.

Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Yao Jin <yao.jin@xxxxxxxxxxxxxxx>
Signed-off-by: Milian Wolff <milian.wolff@xxxxxxxx>
---
 tools/perf/util/callchain.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index 9ab68682c6d0..295f0846fd84 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -642,13 +642,22 @@ static enum match_result match_chain_strings(const char *left,
 static enum match_result match_chain_srcline(struct callchain_cursor_node *node,
 					     struct callchain_list *cnode)
 {
-	char *left = get_srcline(cnode->ms.map->dso,
-				 map__rip_2objdump(cnode->ms.map, cnode->ip),
-				 cnode->ms.sym, true, false);
-	char *right = get_srcline(node->map->dso,
-				  map__rip_2objdump(node->map, node->ip),
-				  node->sym, true, false);
-	enum match_result ret = match_chain_strings(left, right);
+	char *left = NULL;
+	char *right = NULL;
+	enum match_result ret = MATCH_ERROR;
+
+	if (!node->map || !cnode->ms.map)
+		return ret;
+
+	left = get_srcline(cnode->ms.map->dso,
+			   map__rip_2objdump(cnode->ms.map, cnode->ip),
+			   cnode->ms.sym, true, false);
+
+	right = get_srcline(node->map->dso,
+			    map__rip_2objdump(node->map, node->ip),
+			    node->sym, true, false);
+
+	ret = match_chain_strings(left, right);
 
 	free_srcline(left);
 	free_srcline(right);
-- 
2.12.2