On 06/14/16 at 10:41pm, Willy Tarreau wrote: > On Tue, Jun 14, 2016 at 01:19:06PM -0700, Andrew Morton wrote: > > On Sat, 11 Jun 2016 03:33:08 +0200 Heinrich Schuchardt <[email protected]> > > wrote: > > > > > An undetected overflow may occur in do_proc_dointvec_minmax_conv_param. > > > > > > ... > > > > > > --- a/kernel/sysctl.c > > > +++ b/kernel/sysctl.c > > > @@ -2313,7 +2313,17 @@ static int do_proc_dointvec_minmax_conv(bool > > > *negp, unsigned long *lvalp, > > > { > > > struct do_proc_dointvec_minmax_conv_param *param = data; > > > if (write) { > > > - int val = *negp ? -*lvalp : *lvalp; > > > + int val; > > > + > > > + if (*negp) { > > > + if (*lvalp > (unsigned long) INT_MAX + 1) > > > + return -EINVAL; > > > + val = -*lvalp; > > > + } else { > > > + if (*lvalp > (unsigned long) INT_MAX) > > > + return -EINVAL; > > > + val = *lvalp; > > > + } > > > if ((param->min && *param->min > val) || > > > (param->max && *param->max < val)) > > > return -EINVAL; > > > > hm. > > > > What happens if someone does > > > > echo -1 > /proc/foo > > > > expecting to get 0xffffffff? That's a reasonable shorthand, and if we > > change that to spit out EINVAL then people's stuff may break. > > I'd go even further, I don't see anymore how it becomes possible > to actually *write* 0xffffffff at all! This function is used by > proc_dointvec_minmax() which is used with extra1=&zero and extra2 > not set with some unsigned ints to allow the full range to be > configured (eg: dirty_expire_interval is the first I found by a > quick random look).
sysctl_writes_strict use extra1 = -1 and extra2 = 1 But I do not get why -1 does not work, 1 < (unsigned long) INT_MAX + 1 so val = -1, it is still right? > > So for me this change is bogus. > > Willy > Thanks Dave
