Messages in this thread | | | From | Ilias Apalodimas <> | Date | Thu, 8 Jul 2021 19:30:31 +0300 | Subject | Re: [PATCH] skbuff: Fix a potential race while recycling page_pool packets |
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+cc Alexander on his gmail address since the Intel one bounced.
Alexander want me to respin it with you gmail address on the Reported-by?
Sorry for the noise /Ilias
On Thu, 8 Jul 2021 at 19:24, Ilias Apalodimas <ilias.apalodimas@linaro.org> wrote: > > As Alexander points out, when we are trying to recycle a cloned/expanded > SKB we might trigger a race. The recycling code relies on the > pp_recycle bit to trigger, which we carry that over to cloned SKBs. > When that cloned SKB gets expanded, we are creating 2 separate instances > accessing the page frags. Since the skb_release_data() will first try to > recycle the frags, there's a potential race between the original and > cloned SKB. > > Fix this by explicitly making the cloned/expanded SKB not recyclable. > If the original SKB is freed first the pages are released. > If it is released after the clone/expended skb then it can still be > recycled. > > Fixes: 6a5bcd84e886 ("page_pool: Allow drivers to hint on SKB recycling") > Reported-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org> > --- > net/core/skbuff.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 12aabcda6db2..0cb53c05ed76 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -1718,6 +1718,13 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > } > off = (data + nhead) - skb->head; > > + /* If it's a cloned skb we expand with frags attached we must prohibit > + * the recycling code from running, otherwise we might trigger a race > + * while trying to recycle the fragments from the original and cloned > + * skb > + */ > + if (skb_cloned(skb)) > + skb->pp_recycle = 0; > skb->head = data; > skb->head_frag = 0; > skb->data += off; > -- > 2.32.0.rc0 >
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