Re: Serious bug in recent Linux kernels

Dan Kegel (dank@alumni.caltech.edu)
Sun, 10 Jan 1999 18:22:15 -0800

Guest section DW schrieb:
> ... must not produce a negative timeout. The change below makes sure of that ...
>
> + if (timeout > 0)
> + timeout = (timeout*HZ+999)/1000+1;
> if (timeout < 0)
> timeout = MAX_SCHEDULE_TIMEOUT;
> - else if (timeout)
> - timeout = (timeout*HZ+999)/1000+1;
>
> [the expression (timeout*HZ+999)/1000+1 is also a bit peculiar,
> but I have not changed it]

timeout*HZ can overflow and produce a bad positive result for
some values of timeout, I think. Assuming timeout is
a long (I don't have the source handy), how about
if ((timeout < 0) || (timeout > LONG_MAX/HZ))
timeout = MAX_SCHEDULE_TIMEOUT;
else if (timeout > 0)
timeout = (timeout*HZ+999)/1000+1;
?
- Dan

-- 
Speaking only for myself, not for my employer


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