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authorRusty Russell <rusty@rustcorp.com.au>2008-06-23 13:55:38 +1000
committerIngo Molnar <mingo@elte.hu>2008-06-23 22:57:56 +0200
commit961ccddd59d627b89bd3dc284b6517833bbdf25d (patch)
tree4d755085845b8beeaa0bbc3d3ee66e1ccc4156a8
parent481c5346d0981940ee63037eb53e4e37b0735c10 (diff)
sched: add new API sched_setscheduler_nocheck: add a flag to control access checks
Hidehiro Kawai noticed that sched_setscheduler() can fail in stop_machine: it calls sched_setscheduler() from insmod, which can have CAP_SYS_MODULE without CAP_SYS_NICE. Two cases could have failed, so are changed to sched_setscheduler_nocheck: kernel/softirq.c:cpu_callback() - CPU hotplug callback kernel/stop_machine.c:__stop_machine_run() - Called from various places, including modprobe() Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org Cc: sugita <yumiko.sugita.yf@hitachi.com> Cc: Satoshi OSHIMA <satoshi.oshima.fk@hitachi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--include/linux/sched.h2
-rw-r--r--kernel/sched.c48
-rw-r--r--kernel/softirq.c2
-rw-r--r--kernel/stop_machine.c2
4 files changed, 40 insertions, 14 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index c5d3f84..fe3b9b5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1655,6 +1655,8 @@ extern int can_nice(const struct task_struct *p, const int nice);
extern int task_curr(const struct task_struct *p);
extern int idle_cpu(int cpu);
extern int sched_setscheduler(struct task_struct *, int, struct sched_param *);
+extern int sched_setscheduler_nocheck(struct task_struct *, int,
+ struct sched_param *);
extern struct task_struct *idle_task(int cpu);
extern struct task_struct *curr_task(int cpu);
extern void set_curr_task(int cpu, struct task_struct *p);
diff --git a/kernel/sched.c b/kernel/sched.c
index b048ad8..8d7c246 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4746,16 +4746,8 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
set_load_weight(p);
}
-/**
- * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
- * @p: the task in question.
- * @policy: new policy.
- * @param: structure containing the new RT priority.
- *
- * NOTE that the task may be already dead.
- */
-int sched_setscheduler(struct task_struct *p, int policy,
- struct sched_param *param)
+static int __sched_setscheduler(struct task_struct *p, int policy,
+ struct sched_param *param, bool user)
{
int retval, oldprio, oldpolicy = -1, on_rq, running;
unsigned long flags;
@@ -4787,7 +4779,7 @@ recheck:
/*
* Allow unprivileged RT tasks to decrease priority:
*/
- if (!capable(CAP_SYS_NICE)) {
+ if (user && !capable(CAP_SYS_NICE)) {
if (rt_policy(policy)) {
unsigned long rlim_rtprio;
@@ -4823,7 +4815,8 @@ recheck:
* Do not allow realtime tasks into groups that have no runtime
* assigned.
*/
- if (rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0)
+ if (user
+ && rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0)
return -EPERM;
#endif
@@ -4872,8 +4865,39 @@ recheck:
return 0;
}
+
+/**
+ * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
+ * @p: the task in question.
+ * @policy: new policy.
+ * @param: structure containing the new RT priority.
+ *
+ * NOTE that the task may be already dead.
+ */
+int sched_setscheduler(struct task_struct *p, int policy,
+ struct sched_param *param)
+{
+ return __sched_setscheduler(p, policy, param, true);
+}
EXPORT_SYMBOL_GPL(sched_setscheduler);
+/**
+ * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
+ * @p: the task in question.
+ * @policy: new policy.
+ * @param: structure containing the new RT priority.
+ *
+ * Just like sched_setscheduler, only don't bother checking if the
+ * current context has permission. For example, this is needed in
+ * stop_machine(): we create temporary high priority worker threads,
+ * but our caller might not have that capability.
+ */
+int sched_setscheduler_nocheck(struct task_struct *p, int policy,
+ struct sched_param *param)
+{
+ return __sched_setscheduler(p, policy, param, false);
+}
+
static int
do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 36e0617..afd9120 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -645,7 +645,7 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb,
p = per_cpu(ksoftirqd, hotcpu);
per_cpu(ksoftirqd, hotcpu) = NULL;
- sched_setscheduler(p, SCHED_FIFO, &param);
+ sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
kthread_stop(p);
takeover_tasklets(hotcpu);
break;
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index b7350bb..ba9b205 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -187,7 +187,7 @@ struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
/* One high-prio thread per cpu. We'll do this one. */
- sched_setscheduler(p, SCHED_FIFO, &param);
+ sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
kthread_bind(p, cpu);
wake_up_process(p);
wait_for_completion(&smdata.done);