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SubjectRe: [PATCH] parport/ppdev: fix registration of sysctl entries
On Sun, Jul 06, 2008 at 05:07:02PM +0200, Marcin Slusarz wrote:
> On Sun, Jul 06, 2008 at 01:11:48AM +0100, Al Viro wrote:
> > On Sun, Jul 06, 2008 at 12:51:48AM +0100, Al Viro wrote:
> >
> > > I don't believe that it's right. Note that if you *do* race there, you
> > > are fucked regardless of sysctls - ppdev.c::register_device() racing
> > > with itself will do tons of fun things all by itself (starting with two
> > > threads allocating different pdev and both setting pp->pdev).
>
> I wouldn't call it a race - BKL is protecting multiple ioctl calls, so we
> won't ever claim the device from two different threads.

Yes, we can - register_device() does kmalloc() with GFP_KERNEL, which kills
any protection from BKL. BKL is _not_ providing any kind of exclusion while
you sleep.


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