Messages in this thread | | | Subject | Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL pointer dereference | From | Pekka Enberg <> | Date | Fri, 25 Jul 2008 13:41:56 +0300 |
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On Fri, 2008-07-25 at 10:02 +0200, Dieter Ries wrote: > Pekka Enberg schrieb: > > On Thu, 2008-07-24 at 11:51 -0700, Andrew Morton wrote: > >> On Thu, 24 Jul 2008 16:34:36 +0300 Pekka Enberg <penberg@cs.helsinki.fi> 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@trash.net> > >>>>> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi> > >>>> 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? > > > > Yes, it definitely fixed my issue and I have not encountered > further problems with the patch. The machine > is running fine with it. > > Do I have to explicitly add my > Tested-by: Dieter Ries <clip2@gmx.de> > tag somewhere (if yes, where?) or is this enough for you?
No, that's fine. The people who are merging the patch can pick it up. Thanks a lot for your help!
Pekka
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