[PATCH 1/2 v5] perf sched: fix wrong conversion of task state

[Tomoki Sekiyama]

Currently sched_out_state() converts the prev_state u64 bitmask to a char
using the bitmask as an index, which may cause invalid memory access.
This fixes the issue by using the __ffs() returned value as an index.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@xxxxxxxxxxx>
Fixes: cdce9d738b91e ("perf sched: Add sched latency profiling")
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Acked-by: David Ahern <dsahern@xxxxxxxxx>
---
 tools/perf/builtin-sched.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 0dfe8df..ce9bef6 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -897,9 +897,10 @@ static int thread_atoms_insert(struct perf_sched *sched, struct thread *thread)
 
 static char sched_out_state(u64 prev_state)
 {
-	const char *str = TASK_STATE_TO_CHAR_STR;
+	const char str[] = TASK_STATE_TO_CHAR_STR;
+	unsigned int bit = prev_state ? __ffs(prev_state) + 1 : 0;
 
-	return str[prev_state];
+	return bit < ARRAY_SIZE(str) - 1 ? str[bit] : '?';
 }
 
 static int
-- 
2.7.4