>From 8579fc072fda603c4ae472cc3f0390d61556ac01 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Date: Fri, 5 Dec 2014 21:22:22 +0900
Subject: [PATCH] sched: Fix potential call to __ffs(0) in sched_show_task()
"struct task_struct"->state is "volatile long" and __ffs() warns that
"Undefined if no bit exists, so code should check against 0 first."
Therefore, at expression
state = p->state ? __ffs(p->state) + 1 : 0;
in sched_show_task(), CPU might see "p->state" before "?" as "non-zero"
but "p->state" after "?" as "zero", which could result in
"state >= sizeof(stat_nam)" being true and bogus '?' is printed.
This patch changes "state" from "unsigned int" to "unsigned long" and
save "p->state" before calling __ffs(), in order to avoid potential call
to __ffs(0).
Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
---
kernel/sched/core.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 89e7283..8cb5f9b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4528,9 +4528,10 @@ void sched_show_task(struct task_struct *p)
{
unsigned long free = 0;
int ppid;
- unsigned state;
+ unsigned long state = p->state;
- state = p->state ? __ffs(p->state) + 1 : 0;
+ if (state)
+ state = __ffs(state) + 1;
printk(KERN_INFO "%-15.15s %c", p->comm,
state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
#if BITS_PER_LONG == 32
--
1.7.1
--
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