linux-kernel - Re: [PATCH] sched/cpupri: fix cpupri

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140413094023.47c762fd@gandalf.local.home>
Date:	Sun, 13 Apr 2014 09:40:23 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/cpupri: fix cpupri_find() for high priority tasks

On Wed, 09 Apr 2014 05:50:10 +0200
Mike Galbraith <umgwanakikbuti@...il.com> wrote:

> Hi Steven,
> 
> Seems c92211d9b7727 introduced a buglet.
> 
> --snip--
> 
> Bail on task_pri >= MAX_RT_PRIO excludes userspace prio 98 and 99 tasks,
> which map to 100 and 101 respectively.
> 
> A user reported that given two SCHED_RR tasks, one hog, one light, the light
> task may be stacked on top of the hog iff prio >= 98, latency hit follows.
> 
> Signed-off-by: Mike Galbraith <umgwanakikbuti@...il.com>
> Cc: <stable@...r.kernel.org>
> Fixes: c92211d9b7727 sched/cpupri: Remove the vec->lock
> ---
>  kernel/sched/cpupri.c |    3 ---
>  1 file changed, 3 deletions(-)
> 
> --- a/kernel/sched/cpupri.c
> +++ b/kernel/sched/cpupri.c
> @@ -70,9 +70,6 @@ int cpupri_find(struct cpupri *cp, struc
>  	int idx = 0;
>  	int task_pri = convert_prio(p->prio);
>  
> -	if (task_pri >= MAX_RT_PRIO)
> -		return 0;

task_pri is used as an index into pri_to_cpu. Although I don't see how
this can be called for a non RT task, the safer solution is below.

-- Steve

> -
>  	for (idx = 0; idx < task_pri; idx++) {
>  		struct cpupri_vec *vec  = &cp->pri_to_cpu[idx];
>  		int skip = 0;
> 

>From 606aa467c9a51c09ce4efa320db45eee59a9bd06 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
Date: Sun, 13 Apr 2014 09:34:53 -0400
Subject: [PATCH] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in
 cpupri check

The check at the beginning of cpupri_find() makes sure that the task_pri
variable does not exceed the cp->pri_to_cpu array length. But that length
is CPUPRI_NR_PRIORITIES not MAX_RT_PRIO, where it will miss the last two
priorities in that array.

Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.net

Cc: stable@...r.kernel.org
Reported-by: Mike Galbraith <umgwanakikbuti@...il.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/sched/cpupri.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c
index 8b836b3..557356a 100644
--- a/kernel/sched/cpupri.c
+++ b/kernel/sched/cpupri.c
@@ -70,7 +70,7 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
 	int idx = 0;
 	int task_pri = convert_prio(p->prio);
 
-	if (task_pri >= MAX_RT_PRIO)
+	if (task_pri >= CPUPRI_NR_PRIORITIES)
 		return 0;
 
 	for (idx = 0; idx < task_pri; idx++) {
-- 
1.8.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/