Messages in this thread | | | Date | Wed, 27 Feb 2008 11:05:38 -0800 (PST) | Subject | Re: [BUG] 2.6.25-rc3 hangs in early boot on Sun Ultra5 | From | David Miller <> |
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From: Thomas Gleixner <tglx@linutronix.de> Date: Wed, 27 Feb 2008 09:02:22 +0100 (CET)
> On Tue, 26 Feb 2008, David Miller wrote: > > What the FUTEX checking code is doing now is doing a "user" access > > with set_fs(KERNEL_DS) since it runs from the kernel bootup early init > > sequence. And this is illegal according to the existing checks. > > > > When we do set_fs(KERNEL_DS) then pass a "user" pointer down > > into a system call or something like that, we give it a pointer > > that "cannot fault". So if we get into the fault handling > > path here for a case like that we really do want to scream and > > print out an OOPS message in my opinion. > > So it would be correct to set_fs(USER_DS) then do the check and switch > back to KERNEL_DS ?
No, I'm saying it would be better not to take faults purposefully in the kernel address space. We don't have a usable user address space setup at this point in the boot, so using USER_DS would be even worse.
I think I'll just add a different version of the sanity check to this sparc64 code later on, one that will take into consideration this KERNEL_DS case because I can see how it could be useful in other circumstances.
> > Did this FUTEX change go into -stable too? > > It's queued, AFAIK
Crap, I'll need to push my fix there too.
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