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net: gro: don't merge zcopy skbs

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skb_gro_receive() can currently copy frags between the source and GRO
skb, without checking the zerocopy status, and in particular the
SKBFL_MANAGED_FRAG_REFS flag.

When SKBFL_MANAGED_FRAG_REFS is set, the skb doesn't hold a reference
on the pages in shinfo->frags. Appending those frags to another skb's
frags without fixing up the page refcount can lead to UAF.

When either the last skb in the GRO chain (the one we would append
frags to) or the source skb is zerocopy, don't merge the skbs.

Fixes: 753f1ca4e1 ("net: introduce managed frags infrastructure")
Reported-by: Huzaifa Sidhpurwala <huzaifas@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/c3b7f906bbfcbdfd7b4fa9d6c18a438870df85be.1779307748.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Sabrina Dubroca 2026-05-20 22:44:42 +02:00 committed by Jakub Kicinski
parent 3d4432d34c
commit 4db79a322d
1 changed files with 3 additions and 0 deletions
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3
net/core/gro.c
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@ -109,6 +109,9 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
if (p->pp_recycle != skb->pp_recycle)
return -ETOOMANYREFS;
if (skb_zcopy(p) || skb_zcopy(skb))
return -ETOOMANYREFS;
if (unlikely(p->len + len >= netif_get_gro_max_size(p->dev, p) ||
NAPI_GRO_CB(skb)->flush))
return -E2BIG;