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SubjectRe: [patch 1/2] sched: Protect task->cpus_allowed access in sched_getaffinity()
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On Tue, 2009-12-08 at 20:24 +0000, Thomas Gleixner wrote:
> plain text document attachment
> (sched-fix-sched-get-affinity-racy-access.patch)
> sched_getaffinity() is not protected against a concurrent modification
> of the tasks affinity.
>
> Serialize the access with task_rq_lock(task).
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> kernel/sched.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> Index: linux-2.6-tip/kernel/sched.c
> ===================================================================
> --- linux-2.6-tip.orig/kernel/sched.c
> +++ linux-2.6-tip/kernel/sched.c
> @@ -6631,6 +6631,8 @@ SYSCALL_DEFINE3(sched_setaffinity, pid_t
> long sched_getaffinity(pid_t pid, struct cpumask *mask)
> {
> struct task_struct *p;
> + unsigned long flags;
> + struct rq *rq;
> int retval;
>
> get_online_cpus();
> @@ -6645,7 +6647,9 @@ long sched_getaffinity(pid_t pid, struct
> if (retval)
> goto out_unlock;
>
> + rq = task_rq_lock(p, &flags);
> cpumask_and(mask, &p->cpus_allowed, cpu_online_mask);
> + task_rq_unlock(rq, &flags);
>
> out_unlock:
> read_unlock(&tasklist_lock);
>

Hehe, I wrote the exact same patch last night :-)

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>



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