Re: [PATCH] [request for inclusion] Realtime LSM

Matt Mackall
2005-03-08T04:35:10Z

On Mon, Mar 07, 2005 at 07:50:20PM -0800, Andrew Morton wrote:
>
> So I still have the rt-lsm patch floating about, saying "merge me, merge
> me!". I'm not sure that the world would end were I to do so.
>
> Consider this a prod in the direction of those who were pushing
> alternatives ;)

I think Chris Wright's last rlimit patch is more sensible and ready to
go. And I think I may have even convinced Ingo on this point before
the conversation died last time around. So here's that patch again,
updated to 2.6.11. Compiles cleanly. Chris, please add a signed-off-by.

<snip>

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.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: rlimits/include/linux/sched.h
===================================================================
--- rlimits.orig/include/linux/sched.h 2005-03-03 22:50:14.000000000 -0800
+++ rlimits/include/linux/sched.h 2005-03-07 20:18:30.000000000 -0800
@@ -791,6 +791,7 @@ 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 *);
Index: rlimits/kernel/sched.c
===================================================================
--- rlimits.orig/kernel/sched.c 2005-03-02 22:51:08.000000000 -0800
+++ rlimits/kernel/sched.c 2005-03-07 20:23:17.000000000 -0800
@@ -3273,6 +3273,19 @@ 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

/*
@@ -3292,12 +3305,8 @@ 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;

@@ -3307,6 +3316,9 @@ 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;
@@ -3422,6 +3434,7 @@ 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) &&
Index: rlimits/kernel/sys.c
===================================================================
--- rlimits.orig/kernel/sys.c 2005-03-02 22:51:07.000000000 -0800
+++ rlimits/kernel/sys.c 2005-03-07 20:18:30.000000000 -0800
@@ -225,7 +225,7 @@ static int set_one_prio(struct task_stru
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;
}
Index: rlimits/include/asm-generic/resource.h
===================================================================
--- rlimits.orig/include/asm-generic/resource.h 2005-03-02 18:30:27.000000000 -0800
+++ rlimits/include/asm-generic/resource.h 2005-03-07 20:21:04.000000000 -0800
@@ -20,8 +20,10 @@
#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 RLIM_NLIMITS 13
+#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 15
#endif

/*
@@ -53,6 +55,8 @@
[RLIMIT_LOCKS] = { RLIM_INFINITY, RLIM_INFINITY }, \
[RLIMIT_SIGPENDING] = { MAX_SIGPENDING, MAX_SIGPENDING }, \
[RLIMIT_MSGQUEUE] = { MQ_BYTES_MAX, MQ_BYTES_MAX }, \
+ [RLIMIT_NICE] = { 0, 0 }, \
+ [RLIMIT_RTPRIO] = { 0, 0 }, \
}

#endif /* __KERNEL__ */

--
Mathematics is the supreme nostalgia of our time.