sched: Protect task->cpus_allowed access in sched_getaffinity()

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>
Acked-by: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20091208202026.769251187@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 281da29d080192c8924d444eed5fc75adacf5492..c4635f74540c367f873555dc01fd28fcdfae9a4f 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6631,6 +6631,8 @@ SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
 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 cpumask *mask)
        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);