redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

sched/debug: 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-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/201412052131.GCE35924.FVHFOtLOJOMQFS@I-love.SAKURA.ne.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Tetsuo Handa 2014-12-05 21:22:22 +09:00 committed by Ingo Molnar
parent a8b686b3af
commit 1f8a763309
1 changed files with 3 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/sched/core.c
View File

@ -4508,9 +4508,10 @@ 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