Reduce minimal time intervals of setitimer(2) from 1/HZ to 1/(16*HZ) by
using callout_reset_sbt() instead of callout_reset(). We can't remove lower limit completely in this case because of significant processing overhead, caused by unability to use direct callout execution due to using process mutex in callout handler for sending SEGALRM signal. With support of periodic events that would allow unprivileged user to abuse the system. Reviewed by: davide
This commit is contained in:
parent
0e7919f704
commit
b5ea3779da
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=247903
@ -691,7 +691,7 @@ kern_getitimer(struct thread *td, u_int which, struct itimerval *aitv)
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*aitv = p->p_realtimer;
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PROC_UNLOCK(p);
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if (timevalisset(&aitv->it_value)) {
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getmicrouptime(&ctv);
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microuptime(&ctv);
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if (timevalcmp(&aitv->it_value, &ctv, <))
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timevalclear(&aitv->it_value);
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else
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@ -736,28 +736,33 @@ kern_setitimer(struct thread *td, u_int which, struct itimerval *aitv,
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{
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struct proc *p = td->td_proc;
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struct timeval ctv;
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sbintime_t sbt, pr;
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if (aitv == NULL)
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return (kern_getitimer(td, which, oitv));
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if (which > ITIMER_PROF)
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return (EINVAL);
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if (itimerfix(&aitv->it_value))
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if (itimerfix(&aitv->it_value) ||
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aitv->it_value.tv_sec > INT32_MAX / 2)
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return (EINVAL);
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if (!timevalisset(&aitv->it_value))
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timevalclear(&aitv->it_interval);
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else if (itimerfix(&aitv->it_interval))
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else if (itimerfix(&aitv->it_interval) ||
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aitv->it_interval.tv_sec > INT32_MAX / 2)
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return (EINVAL);
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if (which == ITIMER_REAL) {
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PROC_LOCK(p);
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if (timevalisset(&p->p_realtimer.it_value))
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callout_stop(&p->p_itcallout);
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getmicrouptime(&ctv);
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microuptime(&ctv);
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if (timevalisset(&aitv->it_value)) {
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callout_reset(&p->p_itcallout, tvtohz(&aitv->it_value),
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realitexpire, p);
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pr = tvtosbt(aitv->it_value) >> tc_precexp;
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timevaladd(&aitv->it_value, &ctv);
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sbt = tvtosbt(aitv->it_value);
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callout_reset_sbt(&p->p_itcallout, sbt, pr,
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realitexpire, p, C_ABSOLUTE);
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}
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*oitv = p->p_realtimer;
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p->p_realtimer = *aitv;
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@ -793,7 +798,8 @@ void
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realitexpire(void *arg)
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{
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struct proc *p;
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struct timeval ctv, ntv;
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struct timeval ctv;
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sbintime_t isbt;
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p = (struct proc *)arg;
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kern_psignal(p, SIGALRM);
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@ -803,19 +809,17 @@ realitexpire(void *arg)
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wakeup(&p->p_itcallout);
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return;
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}
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for (;;) {
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isbt = tvtosbt(p->p_realtimer.it_interval);
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if (isbt >= sbt_timethreshold)
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getmicrouptime(&ctv);
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else
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microuptime(&ctv);
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do {
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timevaladd(&p->p_realtimer.it_value,
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&p->p_realtimer.it_interval);
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getmicrouptime(&ctv);
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if (timevalcmp(&p->p_realtimer.it_value, &ctv, >)) {
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ntv = p->p_realtimer.it_value;
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timevalsub(&ntv, &ctv);
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callout_reset(&p->p_itcallout, tvtohz(&ntv) - 1,
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realitexpire, p);
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return;
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}
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}
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/*NOTREACHED*/
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} while (timevalcmp(&p->p_realtimer.it_value, &ctv, <=));
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callout_reset_sbt(&p->p_itcallout, tvtosbt(p->p_realtimer.it_value),
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isbt >> tc_precexp, realitexpire, p, C_ABSOLUTE);
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}
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/*
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@ -830,8 +834,9 @@ itimerfix(struct timeval *tv)
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if (tv->tv_sec < 0 || tv->tv_usec < 0 || tv->tv_usec >= 1000000)
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return (EINVAL);
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if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
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tv->tv_usec = tick;
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if (tv->tv_sec == 0 && tv->tv_usec != 0 &&
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tv->tv_usec < (u_int)tick / 16)
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tv->tv_usec = (u_int)tick / 16;
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return (0);
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}
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