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[PATCH] nice and rt-prio rlimits

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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: Matt Mackall <mpm@selenic.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Matt Mackall 2005-05-01 08:59:00 -07:00 committed by Linus Torvalds
parent 9fc1427a01
commit e43379f10b
4 changed files with 27 additions and 8 deletions
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7
include/asm-generic/resource.h
View file

@ -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__ */

1
include/linux/sched.h
View file

@ -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 *);

25
kernel/sched.c
View file

@ -3223,6 +3223,19 @@ void set_user_nice(task_t *p, long nice)
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;
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 @@ int sched_setscheduler(struct task_struct *p, int policy, struct sched_param *pa
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) &&

2
kernel/sys.c
View file

@ -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;
}