Messages in this thread |  | | Date | Sun, 25 Sep 2022 17:41:23 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v2 04/16] skbuff: Phase out ksize() fallback for frag_size |
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On Sun, Sep 25, 2022 at 09:17:40AM +0200, Paolo Abeni wrote: > On Fri, 2022-09-23 at 13:28 -0700, Kees Cook wrote: > > All callers of APIs that allowed a 0-sized frag_size appear to be > > passing actual size information already > > AFAICS, not yet: > > drivers/net/ethernet/qlogic/qed/qed_ll2.c: > skb = build_skb(buffer->data, 0); // -> __build_skb(..., 0) > // -> __build_skb_around() > > drivers/net/ethernet/broadcom/bnx2.c: > skb = build_skb(data, 0); > > I guess some more drivers have calls leading to > > __build_skb_around(..., 0) > > there are several call path to checks...
Ah-ha! Thank you. I will try to hunt these down -- I think we can't remove the "secret resizing" effect of ksize() without fixing these.
> > [...] > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > > index 0b30fbdbd0d0..84ca89c781cd 100644 > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -195,7 +195,11 @@ static void __build_skb_around(struct sk_buff *skb, void *data, > > unsigned int frag_size) > > { > > struct skb_shared_info *shinfo; > > - unsigned int size = frag_size ? : ksize(data); > > + unsigned int size = frag_size; > > + > > + /* All callers should be setting frag size now? */ > > + if (WARN_ON_ONCE(size == 0)) > > + size = ksize(data); > > At some point in the future, I guess we could even drop this check, > right?
Alternatively, we might be able to ask the slab if "data" came from kmalloc or a kmem_cache, and if the former, do:
data = krealloc(kmalloc_size_roundup(ksize(data), ...)
But that seems ugly...
-- Kees Cook
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