Messages in this thread | | | Date | Sat, 18 Mar 2006 13:09:25 -0800 | From | Andrew Morton <> | Subject | Re: [patch 1/2] Validate itimer timeval from userspace |
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Thomas Gleixner <tglx@linutronix.de> wrote: > > 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. >
It would be strange to set an alarm for 0xffffffff seconds in the future but yeah, unless we can point at a reason why nobody could have ever been doing that, we should turn this into permanent, documented behaviour of Linux 2.6 and earlier, I'm afraid.
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