Re: [regression] nf_iterate(), BUG: unable to handle kernel NULLpointer dereference

[Pekka Enberg]

On Thu, 2008-07-24 at 11:51 -0700, Andrew Morton wrote:
> On Thu, 24 Jul 2008 16:34:36 +0300 Pekka Enberg <penberg@xxxxxxxxxxxxxx> wrote:
> 
> > > >> Your patch introduced a use-after-free and double-free.
> > > >> krealloc() frees the old pointer, but it is still used
> > > >> for the ->move operations, then freed again.
> > > >>
> > > >> To fix this I think we need a __krealloc() that doesn't
> > > >> free the old memory, especially since it must not be
> > > >> freed immediately because it may still be used in a RCU
> > > >> read side (see the last part in the patch attached to
> > > >> this mail (based on a kernel without your patch)).
> > > > 
> > > > Agreed. Something like this, perhaps?
> > > > 
> > > > [PATCH] netfilter: fix double-free and use-after free
> > > > 
> > > > As suggested by Patrick McHardy, introduce a __krealloc() that doesn't
> > > > free the original buffer to fix a double-free and use-after-free bug
> > > > introduced by me in netfilter that uses RCU.
> > > > 
> > > > Reported-by: Patrick McHardy <kaber@xxxxxxxxx>
> > > > Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
> > > 
> > > Looks good to me, thanks.
> > 
> > Ingo, can you please test this? Andrew, I'm at OLS so can you pick up
> > the patch in your tree?
> 
> Sure.  Or Patrick can do so and it can be merged via the net tree.
> 
> Ingo, did this patch actually fix something over there?

Apparently it didn't but it did fix Dieter's problem:

http://lkml.org/lkml/2008/7/24/337

Dieter, can we add a Tested-by tag from you to this patch?

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