[PATCH 2/2] perf, tools: Avoid segfault on alias parse error

[Andi Kleen]

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

When there is a parse error on adding an alias the parser
segfaults. It thinks data is a parse_events_evlist and tries
to reference the error member. But it's really a parse_events_terms
for this call path through parse_events_terms.

Add the error member at the same location in parse_events_terms
as in *_evlist and set up a error structure to report errors correctly.

This can be only reproduced by adding errors to JSON aliases.

Segfault:

    #'0  0x00000000004d66d2 in parse_events_evlist_error (data=0x7fffffffce20, idx=6, str=0x76cda8 "parser error") at util/parse-events.c:2530
    #'1  0x0000000000516d0a in parse_events_error (loc=0x7fffffffb210, data=0x7fffffffce20, scanner=0x245b400, msg=0x76cb13 "syntax error") at util/parse-events.y:692
    #'2  0x000000000051675b in parse_events_parse (_data=0x7fffffffce20, scanner=0x245b400) at /home/ak/hle/obj-perf/util/parse-events-bison.c:2213
    #'3  0x00000000004d3fd6 in parse_events__scanner (str=0x725cff "event=0,", data=0x7fffffffce20, start_token=259) at util/parse-events.c:1646
    #'4  0x00000000004d4063 in parse_events_terms (terms=0x245b398, str=0x725cff "event=0,") at util/parse-events.c:1664
    #'5  0x00000000005179f1 in __perf_pmu__new_alias (list=0x7fffffffcf90, dir=0x0, name=0x725cec "unc_cha_clockticks", desc=0x725d08 "Uncore cache clock ticks. Unit: uncore_cha ",
    val=0x725cff "event=0,", long_desc=0x0, topic=0x725d34 "uncore other", unit=0x0, perpkg=0x6ca7c6 "1", metric_expr=0x0, metric_name=0x0) at util/pmu.c:255
    #'6  0x0000000000518789 in pmu_add_cpu_aliases (head=0x7fffffffcf90, name=0x2450903 "uncore_cha_9") at util/pmu.c:571
    #'7  0x00000000005188ac in pmu_lookup (name=0x2450903 "uncore_cha_9") at util/pmu.c:613
    #'8  0x0000000000518aff in perf_pmu__find (name=0x2450903 "uncore_cha_9") at util/pmu.c:672
    #'9  0x00000000005183d5 in pmu_read_sysfs () at util/pmu.c:467
    #'10 0x0000000000518a54 in perf_pmu__scan (pmu=0x0) at util/pmu.c:651
    #'11 0x0000000000519f26 in print_pmu_events (event_glob=0x0, name_only=false, quiet_flag=false, long_desc=false, details_flag=false) at util/pmu.c:1173
    #'12 0x00000000004d5ef0 in print_events (event_glob=0x0, name_only=false, quiet_flag=false, long_desc=false, details_flag=false) at util/parse-events.c:2343
    #'13 0x000000000043c7d4 in cmd_list (argc=0, argv=0x7fffffffeb90) at builtin-list.c:56
    #'14 0x00000000004ab2c8 in run_builtin (p=0xa281a0 <commands+192>, argc=1, argv=0x7fffffffeb90) at perf.c:296
    #15 0x00000000004ab535 in handle_internal_command (argc=1, argv=0x7fffffffeb90) at perf.c:348
    #16 0x00000000004ab687 in run_argv (argcp=0x7fffffffe9ec, argv=0x7fffffffe9e0) at perf.c:392
    #17 0x00000000004aba55 in main (argc=1, argv=0x7fffffffeb90) at perf.c:530

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
 tools/perf/util/parse-events.c | 2 ++
 tools/perf/util/parse-events.h | 4 +++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 84e301073885..15b472aec767 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1656,7 +1656,9 @@ static int parse_events__scanner(const char *str, void *data, int start_token)
  */
 int parse_events_terms(struct list_head *terms, const char *str)
 {
+	struct parse_events_error err = { .idx = 0, };
 	struct parse_events_terms data = {
+		.error = &err,
 		.terms = NULL,
 	};
 	int ret;
diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index a235f4d6d5e5..de217f5b37bb 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -108,15 +108,17 @@ struct parse_events_error {
 	char *help;	/* optional help string */
 };
 
+/* error field must match parse_events_terms */
 struct parse_events_evlist {
+	struct parse_events_error *error;
 	struct list_head	   list;
 	int			   idx;
 	int			   nr_groups;
-	struct parse_events_error *error;
 	struct perf_evlist	  *evlist;
 };
 
 struct parse_events_terms {
+	struct parse_events_error *error;
 	struct list_head *terms;
 };
 
-- 
2.9.4