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SubjectRe: [PATCH] Fix guest memory leak and panic
Ian Campbell <> wrote on 10/18/2011 02:06:56 PM:

Hi Ian,

> On Tue, 2011-10-18 at 09:05 +0100, Krishna Kumar wrote:
> > The extra reference to the fragment pages causes those pages to
> > not get freed in skb_release_data(). The following patch fixes
> > the bug. I have not checked if any other converted driver has
> > the same issue.
> Damn. You are completely correct and I appear to have made this same
> mistake several times. A quick look suggests that at least cxbg,
> myriage, vmxnet, cassini and bnx2 may potentially have a similar
> issue :-( (I stopped looking at that point, I'll obviously do a full
> audit).
> I considered quite carefully whether (__)skb_frag_set_page should take a
> reference or not and decided yes but I'm starting to reconsider whether
> I made the right choice. It seems that is just confusing and violates
> the principal of least surprise to have a function called "set" take a
> new reference. In reality all existing drivers expect that adding a page
> to an SKB frag will just take over the existing reference.
> I think the best thing might be to remove the additional ref taking from
> the setter function and audit the previous changes to ensure they
> conform. I'll do that right away and post a fixup patch ASAP.
> > Signed-off-by: Krishna Kumar <>
> This change is correct as things stand today, so:
> Acked-by: Ian Campbell <>
> but perhaps it would be better to hold off and let me fix all of these
> all at once.

Either way is fine with me. However, besides having a fix,
I would like to remove the manual initializations in
set_skb_frag(), and substitute with __skb_fill_page_desc,
like other drivers do.


- KK

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