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

commit 3160568371da441b7f2fb57f2f1225404207e8f2 upstream

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>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/sched.c b/kernel/sched.c
index 48f8dc07648ddb5bdc027b3a1fa2c3dcb6c7f3c0..eaf30be616e554b1a435092943e1eb63cb3833b5 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6686,6 +6686,8 @@ 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();
@@ -6700,7 +6702,9 @@ 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);