[PATCH 4.16 159/272] perf stat: Fix core dump when flag T is used

Greg Kroah-Hartman
2018-05-28T11:11:18Z

From: Thomas Richter <tmricht@linux.vnet.ibm.com>

[ Upstream commit fca32340a5e8b896f57d41fd94b8b1701df25eb1 ]

Executing command 'perf stat -T -- ls' dumps core on x86 and s390.

Here is the call back chain (done on x86):

# gdb ./perf
....
(gdb) r stat -T -- ls
...
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff56d1963 in vasprintf () from /lib64/libc.so.6
(gdb) where
#0 0x00007ffff56d1963 in vasprintf () from /lib64/libc.so.6
#1 0x00007ffff56ae484 in asprintf () from /lib64/libc.so.6
#2 0x00000000004f1982 in __parse_events_add_pmu (parse_state=0x7fffffffd580,
list=0xbfb970, name=0xbf3ef0 "cpu",
head_config=0xbfb930, auto_merge_stats=false) at util/parse-events.c:1233
#3 0x00000000004f1c8e in parse_events_add_pmu (parse_state=0x7fffffffd580,
list=0xbfb970, name=0xbf3ef0 "cpu",
head_config=0xbfb930) at util/parse-events.c:1288
#4 0x0000000000537ce3 in parse_events_parse (_parse_state=0x7fffffffd580,
scanner=0xbf4210) at util/parse-events.y:234
#5 0x00000000004f2c7a in parse_events__scanner (str=0x6b66c0
"task-clock,{instructions,cycles,cpu/cycles-t/,cpu/tx-start/}",
parse_state=0x7fffffffd580, start_token=258) at util/parse-events.c:1673
#6 0x00000000004f2e23 in parse_events (evlist=0xbe9990, str=0x6b66c0
"task-clock,{instructions,cycles,cpu/cycles-t/,cpu/tx-start/}", err=0x0)
at util/parse-events.c:1713
#7 0x000000000044e137 in add_default_attributes () at builtin-stat.c:2281
#8 0x000000000044f7b5 in cmd_stat (argc=1, argv=0x7fffffffe3b0) at
builtin-stat.c:2828
#9 0x00000000004c8b0f in run_builtin (p=0xab01a0 <commands+288>, argc=4,
argv=0x7fffffffe3b0) at perf.c:297
#10 0x00000000004c8d7c in handle_internal_command (argc=4,
argv=0x7fffffffe3b0) at perf.c:349
#11 0x00000000004c8ece in run_argv (argcp=0x7fffffffe20c,
argv=0x7fffffffe200) at perf.c:393
#12 0x00000000004c929c in main (argc=4, argv=0x7fffffffe3b0) at perf.c:537
(gdb)

It turns out that a NULL pointer is referenced. Here are the
function calls:

...
cmd_stat()
+---> add_default_attributes()
+---> parse_events(evsel_list, transaction_attrs, NULL);
3rd parameter set to NULL

Function parse_events(xx, xx, struct parse_events_error *err) dives
into a bison generated scanner and creates
parser state information for it first:

struct parse_events_state parse_state = {
.list = LIST_HEAD_INIT(parse_state.list),
.idx = evlist->nr_entries,
.error = err, <--- NULL POINTER !!!
.evlist = evlist,
};

Now various functions inside the bison scanner are called to end up in
__parse_events_add_pmu(struct parse_events_state *parse_state, ..) with
first parameter being a pointer to above structure definition.

Now the PMU event name is not found (because being executed in a VM) and
this function tries to create an error message with

asprintf(&parse_state->error.str, ....)

which references a NULL pointer and dumps core.

Fix this by providing a pointer to the necessary error information
instead of NULL. Technically only the else part is needed to avoid the
core dump, just lets be safe...

Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Link: http://lkml.kernel.org/r/20180308145735.64717-1-tmricht@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/perf/builtin-stat.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -2274,11 +2274,16 @@ static int add_default_attributes(void)
return 0;

if (transaction_run) {
+ struct parse_events_error errinfo;
+
if (pmu_have_event("cpu", "cycles-ct") &&
pmu_have_event("cpu", "el-start"))
- err = parse_events(evsel_list, transaction_attrs, NULL);
+ err = parse_events(evsel_list, transaction_attrs,
+ &errinfo);
else
- err = parse_events(evsel_list, transaction_limited_attrs, NULL);
+ err = parse_events(evsel_list,
+ transaction_limited_attrs,
+ &errinfo);
if (err) {
fprintf(stderr, "Cannot set up transaction events\n");
return -1;