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SubjectRe: [PATCH] Reset file->f_op in snd_card_file_remove(). Take 2
At Fri, 29 Sep 2006 14:29:20 +0200,
Karsten Wiese wrote:
>
> Am Freitag, 29. September 2006 12:48 schrieb Takashi Iwai:
> > At Thu, 28 Sep 2006 22:28:02 +0200,
> > Karsten Wiese wrote:
> > >
> > > Hi
> > >
> > > It oopses with 2.6.18-rt4 + alsa-kernel-1.0.13rc3 now.
> > > I wrote before, 2.6.18-rt3 + alsa-driver-1.0.13rc3 would be ok,
> > > but its not. bug showed again reliably under memory-pressure.
> > >
> > > Karsten
> > >
> > > ===
> > >
> > > Reset file->f_op in snd_card_file_remove(). Take 2
> > >
> > >
> > > i think what happens here is:
> > >
> > > us428control runs, kernel has allocated a struct file for /dev/hwC1D0.
> > >
> > > usb disconnect
> > >
> > > snd_usb_usx2y calls snd_card_disconnect,
> > > tells us428control to exit.
> > >
> > > snd_card_disconnect replaces /dev/hwC1D0's file->f_op
> > > with a kmalloc()ed version, that would only allow releases.
> > >
> > > us428control starts exiting
> > >
> > > __fput is called with struct file for /dev/hwC1D0.
> > >
> > > snd_card_file_remove() is called, alsa notices struct file
> > > for /dev/hwC1D0 is about to be closed.
> > > with patch below, file->f_op would be set NULL now.
> > >
> > > snd_usb_usx2y's free()s snd_card instance and /dev/hwC1D0's
> > > file->f_ops, those that would only allow releases.
> > >
> > > for reason I would like to know,
> > > __fput is called again with struct file for /dev/hwC1D0
> > > from us428control's do_exit().
> > > __fput see's file->f_op is still set.
> > > Without patch and under memory pressure, file->f_op can
> > > point to anything now.
> > >
> > >
> > > Signed-off-by: Karsten Wiese <annabellesgarden@yahoo.de>
> >
> > I guess this bug is fixed by Florin's patch below, juding from your
> > explanation. Could you check it?
> >
> Florin's patch fixes it.
>
> This one for immediate consumation by mainline, mm, rt,
> and the stable teams, hmm?

It'll be pushed to mainline soon together with other ALSA fixes. Then
I'll forward to stable, too.


Takashi
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