Re: BUG: disk corruption 2.3.99-pre4-pre3

From: Alexander Viro (viro@math.psu.edu)
Date: Thu Apr 06 2000 - 01:05:27 EST


On Wed, 5 Apr 2000, Simon Kirby wrote:

> On Tue, Apr 04, 2000 at 04:19:15PM -0400, Alexander Viro wrote:
>
> > On Tue, 4 Apr 2000, Jeff Garzik wrote:
> >
> > > Copying an ISO from a 2.2.15-pre17 SMP box, over a network, to a
> > > 2.3.99-pre4-pre3 K6 box.
> > >
> > > smpbox> md5sum iso
> > > smpbox> cp iso /remote/tmp
> > > smpbox> md5sum iso # sum matches
> > >
> > > k6box> md5sum iso # sums differ
> >...
> >
> > Hmmm.... looks like somebody moved the locking in do_exit(). WTF?
> > Another problem being that shmfs calls do_mmap() without proper locking,
> > but that's another story.
>
> I assume you're talking about the task_lock in do_exit()? It seems to be
> where Andi Kleen wrote a patch to move it, and CC'd the email to viro@redhat.com
> (attached). The email had subject "task_lock allows denial of service [+PATCH]".

Which bounced, since it's aviro@....
task_lock() was there for purpose, _exactly_ to provide an exclusion with
procfs. Andi just reintroduced a race.

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