d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

libc: Fix possible overflow in binuptime().

Browse Source 
This is an application of the kernel overflow fix from r357948 to
userspace, based on the algorithm developed by Bruce Evans. To keep
the ABI of the vds_timekeep stable, instead of adding the large_delta
member, MSB of both multipliers are added to quickly estimate the overflow.

Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2020-04-09 23:22:35 +00:00
parent c948a17a52
commit 09bae0a023
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=359758
1 changed files with 16 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
lib/libc/sys/__vdso_gettimeofday.c
View File

@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
#include <sys/time.h>
#include <sys/vdso.h>
#include <errno.h>
#include <strings.h>
#include <time.h>
#include <machine/atomic.h>
#include "libc_private.h"
@ -62,7 +63,8 @@ binuptime(struct bintime *bt, struct vdso_timekeep *tk, int abs)
{
struct vdso_timehands *th;
uint32_t curr, gen;
u_int delta;
uint64_t scale, x;
u_int delta, scale_bits;
int error;
do {
@ -78,7 +80,19 @@ binuptime(struct bintime *bt, struct vdso_timekeep *tk, int abs)
continue;
if (error != 0)
return (error);
bintime_addx(bt, th->th_scale * delta);
scale = th->th_scale;
#ifdef _LP64
scale_bits = ffsl(scale);
#else
scale_bits = ffsll(scale);
#endif
if (__predict_false(scale_bits + fls(delta) > 63)) {
x = (scale >> 32) * delta;
scale &= 0xffffffff;
bt->sec += x >> 32;
bintime_addx(bt, x << 32);
}
bintime_addx(bt, scale * delta);
if (abs)
bintime_add(bt, &th->th_boottime);