From: Thomas Gleixner commit 5fe85be081edf0ac92d83f9c39e0ab5c1371eb82 upstream read_lock(&tasklist_lock) does not protect sys_sched_getscheduler and sys_sched_getparam() against a concurrent update of the policy or scheduler parameters as do_sched_setscheduler() does not take the tasklist_lock. The accessed integers can be retrieved w/o locking and are snapshots anyway. Using rcu_read_lock() to protect find_task_by_vpid() and prevent the task struct from going away is not changing the above situation. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra LKML-Reference: <20091209100706.753790977@linutronix.de> Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- kernel/sched.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6505,7 +6505,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_ return -EINVAL; retval = -ESRCH; - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_process_by_pid(pid); if (p) { retval = security_task_getscheduler(p); @@ -6513,7 +6513,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_ retval = p->policy | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0); } - read_unlock(&tasklist_lock); + rcu_read_unlock(); return retval; } @@ -6531,7 +6531,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p if (!param || pid < 0) return -EINVAL; - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_process_by_pid(pid); retval = -ESRCH; if (!p) @@ -6542,7 +6542,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p goto out_unlock; lp.sched_priority = p->rt_priority; - read_unlock(&tasklist_lock); + rcu_read_unlock(); /* * This one might sleep, we cannot do it with a spinlock held ... @@ -6552,7 +6552,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p return retval; out_unlock: - read_unlock(&tasklist_lock); + rcu_read_unlock(); return retval; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/