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    SubjectRe: [patch 1/2] Validate itimer timeval from userspace
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    On Sat, 2006-03-18 at 12:31 -0800, Andrew Morton wrote:
    > Thomas Gleixner <tglx@linutronix.de> wrote:
    > >
    > > On Sat, 2006-03-18 at 12:07 -0800, Andrew Morton wrote:
    > >
    > > > From my reading, 2.4's sys_setitimer() will normalise the incoming timeval
    > > > rather than rejecting it. And I think 2.6.13 did that too.
    > > >
    > > > It would be bad of us to change this behaviour, even if that's what the
    > > > spec says we should do - because we can break existing applications.
    > > >
    > > > So I think we're stuck with it - we should normalise and then accept such
    > > > timevals. And we should have a big comment explaining how we differ from
    > > > the spec, and why.
    > >
    > > Hmm. How do you treat a negative value ?
    > >
    >
    > In the same way as earlier kernels did!
    >
    > Unless, of course, those kernels did something utterly insane. In that
    > case we'd need to have a little think.

    It was caught by:

    timeval_to_jiffies(const struct timeval *value)
    {
    unsigned long sec = value->tv_sec;
    long usec = value->tv_usec;

    if (sec >= MAX_SEC_IN_JIFFIES)
    sec = MAX_SEC_IN_JIFFIES;
    ....
    }

    The conversion of long to unsigned long converted a negative value to
    the maximum timeout.

    It's not utterly insane, but it does not make much sense either.

    Of course I can convert it that way, if we want to keep this "help
    sloppy programmers aid" alive.

    tglx



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