Messages in this thread | | | Subject | Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL pointer dereference | From | Pekka Enberg <> | Date | Thu, 24 Jul 2008 16:34:36 +0300 |
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On Thu, 2008-07-24 at 15:31 +0200, Patrick McHardy wrote: > Pekka Enberg wrote: > > On Thu, 2008-07-24 at 14:49 +0200, Patrick McHardy wrote: > >> Pekka Enberg wrote: > >>> Hmm, why do you think it's related? It looks like elem->hook() is a > >>> NULL pointer but my patch shouldn't make any difference here... > >> No, its already in ipv4_confirm, so its most likely helper->help() > >> thats NULL, which is contained in an extension. > >> > >> The reason why I think its this patch is (quoting from an old > >> email that I never got a response to): > > > > Oh, I'm really sorry about that. > > No problem :) > > >> --- > >> 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?
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