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Prevent overflow for usertime/systime in caclru1

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PR:		76972 and duplicates
Reported by:	Dr. Christopher Landauer <cal AT aero.org>,
		Steinar Haug <sthaug AT nethelp.no>
Submitted by:	Andrey Zonov <andrey AT zonov.org> (earlier version)
MFC after:	2 weeks
This commit is contained in:
Conrad Meyer 2019-02-10 23:07:46 +00:00
parent aac5464b61
commit e0d164c7a6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=343985
1 changed files with 13 additions and 4 deletions
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17
sys/kern/kern_resource.c
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@ -863,6 +863,15 @@ rufetchtd(struct thread *td, struct rusage *ru)
calcru1(p, &td->td_rux, &ru->ru_utime, &ru->ru_stime);
}
static uint64_t
mul64_by_fraction(uint64_t a, uint64_t b, uint64_t c)
{
/*
* Compute floor(a * (b / c)) without overflowing, (b / c) <= 1.0.
*/
return ((a / c) * b + (a % c) * (b / c) + (a % c) * (b % c) / c);
}
static void
calcru1(struct proc *p, struct rusage_ext *ruxp, struct timeval *up,
struct timeval *sp)
@ -892,10 +901,10 @@ calcru1(struct proc *p, struct rusage_ext *ruxp, struct timeval *up,
* The normal case, time increased.
* Enforce monotonicity of bucketed numbers.
*/
uu = (tu * ut) / tt;
uu = mul64_by_fraction(tu, ut, tt);
if (uu < ruxp->rux_uu)
uu = ruxp->rux_uu;
su = (tu * st) / tt;
su = mul64_by_fraction(tu, st, tt);
if (su < ruxp->rux_su)
su = ruxp->rux_su;
} else if (tu + 3 > ruxp->rux_tu || 101 * tu > 100 * ruxp->rux_tu) {
@ -924,8 +933,8 @@ calcru1(struct proc *p, struct rusage_ext *ruxp, struct timeval *up,
"to %ju usec for pid %d (%s)\n",
(uintmax_t)ruxp->rux_tu, (uintmax_t)tu,
p->p_pid, p->p_comm);
uu = (tu * ut) / tt;
su = (tu * st) / tt;
uu = mul64_by_fraction(tu, ut, tt);
su = mul64_by_fraction(tu, st, tt);
}
ruxp->rux_uu = uu;