Commit e43379f1 authored by Matt Mackall's avatar Matt Mackall Committed by Linus Torvalds
Browse files

[PATCH] nice and rt-prio rlimits 

Add a pair of rlimits for allowing non-root tasks to raise nice and rt
priorities. Defaults to traditional behavior. Originally written by
Chris Wright.

The patch implements a simple rlimit ceiling for the RT (and nice) priorities
a task can set.  The rlimit defaults to 0, meaning no change in behavior by
default.  A value of 50 means RT priority levels 1-50 are allowed.  A value of
100 means all 99 privilege levels from 1 to 99 are allowed.  CAP_SYS_NICE is
blanket permission.

(akpm: see http://www.uwsg.iu.edu/hypermail/linux/kernel/0503.1/1921.html

 for
tips on integrating this with PAM).

Signed-off-by: default avatarMatt Mackall <mpm@selenic.com>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 9fc1427a

include/asm-generic/resource.h

+6 −1
Original line number Diff line number Diff line
@@ -41,8 +41,11 @@ 
#define RLIMIT_LOCKS		10	/* maximum file locks held */

#define RLIMIT_SIGPENDING	11	/* max number of pending signals */

#define RLIMIT_MSGQUEUE		12	/* maximum bytes in POSIX mqueues */

#define RLIMIT_NICE		13	/* max nice prio allowed to raise to

					   0-39 for nice level 19 .. -20 */

#define RLIMIT_RTPRIO		14	/* maximum realtime priority */



#define RLIM_NLIMITS		13

#define RLIM_NLIMITS		15



/*

 * SuS says limits have to be unsigned.
@@ -81,6 +84,8 @@ 
	[RLIMIT_LOCKS]		= {  RLIM_INFINITY,  RLIM_INFINITY },	\

	[RLIMIT_SIGPENDING]	= { 		0,	       0 },	\

	[RLIMIT_MSGQUEUE]	= {   MQ_BYTES_MAX,   MQ_BYTES_MAX },	\

	[RLIMIT_NICE]		= { 0, 0 },				\

	[RLIMIT_RTPRIO]		= { 0, 0 },				\

}



#endif	/* __KERNEL__ */

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -845,6 +845,7 @@ extern void sched_idle_next(void); 
extern void set_user_nice(task_t *p, long nice);

extern int task_prio(const task_t *p);

extern int task_nice(const task_t *p);

extern int can_nice(const task_t *p, const int nice);

extern int task_curr(const task_t *p);

extern int idle_cpu(int cpu);

extern int sched_setscheduler(struct task_struct *, int, struct sched_param *);

kernel/sched.c

+19 −6
Original line number Diff line number Diff line
@@ -3223,6 +3223,19 @@ out_unlock: 


EXPORT_SYMBOL(set_user_nice);



/*

 * can_nice - check if a task can reduce its nice value

 * @p: task

 * @nice: nice value

 */

int can_nice(const task_t *p, const int nice)

{

	/* convert nice value [19,-20] to rlimit style value [0,39] */

	int nice_rlim = 19 - nice;

	return (nice_rlim <= p->signal->rlim[RLIMIT_NICE].rlim_cur ||

		capable(CAP_SYS_NICE));

}



#ifdef __ARCH_WANT_SYS_NICE



/*
@@ -3242,12 +3255,8 @@ asmlinkage long sys_nice(int increment) 
	 * We don't have to worry. Conceptually one call occurs first

	 * and we have a single winner.

	 */

	if (increment < 0) {

		if (!capable(CAP_SYS_NICE))

			return -EPERM;

	if (increment < -40)

		increment = -40;

	}

	if (increment > 40)

		increment = 40;
@@ -3257,6 +3266,9 @@ asmlinkage long sys_nice(int increment) 
	if (nice > 19)

		nice = 19;



	if (increment < 0 && !can_nice(current, nice))

		return -EPERM;



	retval = security_task_setnice(current, nice);

	if (retval)

		return retval;
@@ -3372,6 +3384,7 @@ recheck: 
		return -EINVAL;



	if ((policy == SCHED_FIFO || policy == SCHED_RR) &&

	    param->sched_priority > p->signal->rlim[RLIMIT_RTPRIO].rlim_cur &&

	    !capable(CAP_SYS_NICE))

		return -EPERM;

	if ((current->euid != p->euid) && (current->euid != p->uid) &&

kernel/sys.c

+1 −1
Original line number Diff line number Diff line
@@ -227,7 +227,7 @@ static int set_one_prio(struct task_struct *p, int niceval, int error) 
		error = -EPERM;

		goto out;

	}

	if (niceval < task_nice(p) && !capable(CAP_SYS_NICE)) {

	if (niceval < task_nice(p) && !can_nice(p, niceval)) {

		error = -EACCES;

		goto out;

	}

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