[PATCH 5.14 025/172] perf iostat: Fix Segmentation fault from NULL struct perf_counts_values *

[Greg Kroah-Hartman]

From: Like Xu <likexu@xxxxxxxxxxx>

[ Upstream commit 4da8b121884d84476f3d50d46a471471af1aa9df ]

If the 'perf iostat' user specifies two or more iio_root_ports and also
specifies the cpu(s) by -C which is not *connected to all* the above iio
ports, the iostat_print_metric() will run into trouble:

For example:

  $ perf iostat list
  S0-uncore_iio_0<0000:16>
  S1-uncore_iio_0<0000:97> # <--- CPU 1 is located in the socket S0

  $ perf iostat 0000:16,0000:97 -C 1 -- ls
  port 	Inbound Read(MB)	Inbound Write(MB)	Outbound Read(MB)	Outbound
  Write(MB) ../perf-iostat: line 12: 104418 Segmentation fault
  (core dumped) perf stat --iostat$DELIMITER$*

The core-dump stack says, in the above corner case, the returned
(struct perf_counts_values *) count will be NULL, and the caller
iostat_print_metric() apparently doesn't not handle this case.

  433	struct perf_counts_values *count = perf_counts(evsel->counts, die, 0);
  434
  435	if (count->run && count->ena) {
  (gdb) p count
  $1 = (struct perf_counts_values *) 0x0

The deeper reason is that there are actually no statistics from the user
specified pair "iostat 0000:X, -C (disconnected) Y ", but let's fix it with
minimum cost by adding a NULL check in the user space.

Fixes: f9ed693e8bc0e7de ("perf stat: Enable iostat mode for x86 platforms")
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
Cc: Alexander Antonov <alexander.antonov@xxxxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Link: http://lore.kernel.org/lkml/20210927081115.39568-2-likexu@xxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/perf/arch/x86/util/iostat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/arch/x86/util/iostat.c b/tools/perf/arch/x86/util/iostat.c
index eeafe97b8105..792cd75ade33 100644
--- a/tools/perf/arch/x86/util/iostat.c
+++ b/tools/perf/arch/x86/util/iostat.c
@@ -432,7 +432,7 @@ void iostat_print_metric(struct perf_stat_config *config, struct evsel *evsel,
 	u8 die = ((struct iio_root_port *)evsel->priv)->die;
 	struct perf_counts_values *count = perf_counts(evsel->counts, die, 0);
 
-	if (count->run && count->ena) {
+	if (count && count->run && count->ena) {
 		if (evsel->prev_raw_counts && !out->force_header) {
 			struct perf_counts_values *prev_count =
 				perf_counts(evsel->prev_raw_counts, die, 0);
-- 
2.33.0