[PATCH 6.18 374/377] net: gro: dont merge zcopy skbs

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sabrina Dubroca <sd@queasysnail.net>

[ Upstream commit 4db79a322db8c97f7b73b8a347395ef4d685eb40 ]

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: 753f1ca4e1e5 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/gro.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/gro.c b/net/core/gro.c
index 867611d171dbb..b5f790a643d49 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -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;
-- 
2.53.0