diff options
Diffstat (limited to 'sys')
| -rw-r--r-- | sys/kern/kern_resource.c | 58 |
1 files changed, 33 insertions, 25 deletions
diff --git a/sys/kern/kern_resource.c b/sys/kern/kern_resource.c index cccb040..e0bb453 100644 --- a/sys/kern/kern_resource.c +++ b/sys/kern/kern_resource.c @@ -56,6 +56,7 @@ __FBSDID("$FreeBSD$"); #include <sys/sched.h> #include <sys/sx.h> #include <sys/syscallsubr.h> +#include <sys/sysctl.h> #include <sys/sysent.h> #include <sys/time.h> #include <sys/umtx.h> @@ -273,6 +274,10 @@ donice(struct thread *td, struct proc *p, int n) return (0); } +static int unprivileged_idprio; +SYSCTL_INT(_security_bsd, OID_AUTO, unprivileged_idprio, CTLFLAG_RW, + &unprivileged_idprio, 0, "Allow non-root users to set an idle priority"); + /* * Set realtime priority for LWP. */ @@ -321,18 +326,26 @@ sys_rtprio_thread(struct thread *td, struct rtprio_thread_args *uap) break; /* Disallow setting rtprio in most cases if not superuser. */ -/* - * Realtime priority has to be restricted for reasons which should be - * obvious. However, for idle priority, there is a potential for - * system deadlock if an idleprio process gains a lock on a resource - * that other processes need (and the idleprio process can't run - * due to a CPU-bound normal process). Fix me! XXX - */ -#if 0 - if (RTP_PRIO_IS_REALTIME(rtp.type)) { -#else - if (rtp.type != RTP_PRIO_NORMAL) { -#endif + + /* + * Realtime priority has to be restricted for reasons which + * should be obvious. However, for idleprio processes, there is + * a potential for system deadlock if an idleprio process gains + * a lock on a resource that other processes need (and the + * idleprio process can't run due to a CPU-bound normal + * process). Fix me! XXX + * + * This problem is not only related to idleprio process. + * A user level program can obtain a file lock and hold it + * indefinitely. Additionally, without idleprio processes it is + * still conceivable that a program with low priority will never + * get to run. In short, allowing this feature might make it + * easier to lock a resource indefinitely, but it is not the + * only thing that makes it possible. + */ + if (RTP_PRIO_BASE(rtp.type) == RTP_PRIO_REALTIME || + (RTP_PRIO_BASE(rtp.type) == RTP_PRIO_IDLE && + unprivileged_idprio == 0)) { error = priv_check(td, PRIV_SCHED_RTPRIO); if (error) break; @@ -417,19 +430,14 @@ sys_rtprio(td, uap) if ((error = p_cansched(td, p)) || (error = cierror)) break; - /* Disallow setting rtprio in most cases if not superuser. */ -/* - * Realtime priority has to be restricted for reasons which should be - * obvious. However, for idle priority, there is a potential for - * system deadlock if an idleprio process gains a lock on a resource - * that other processes need (and the idleprio process can't run - * due to a CPU-bound normal process). Fix me! XXX - */ -#if 0 - if (RTP_PRIO_IS_REALTIME(rtp.type)) { -#else - if (rtp.type != RTP_PRIO_NORMAL) { -#endif + /* + * Disallow setting rtprio in most cases if not superuser. + * See the comment in sys_rtprio_thread about idprio + * threads holding a lock. + */ + if (RTP_PRIO_BASE(rtp.type) == RTP_PRIO_REALTIME || + (RTP_PRIO_BASE(rtp.type) == RTP_PRIO_IDLE && + !unprivileged_idprio)) { error = priv_check(td, PRIV_SCHED_RTPRIO); if (error) break; |
