[net PATCH] skb: Do mix page pool and page referenced frags in GRO

[Alexander Duyck]

From: Alexander Duyck <alexanderduyck@xxxxxx>

GSO should not merge page pool recycled frames with standard reference
counted frames. Traditionally this didn't occur, at least not often.
However as we start looking at adding support for wireless adapters there
becomes the potential to mix the two due to A-MSDU repartitioning frames in
the receive path. There are possibly other places where this may have
occurred however I suspect they must be few and far between as we have not
seen this issue until now.

Fixes: 53e0961da1c7 ("page_pool: add frag page recycling support in page pool")
Reported-by: Felix Fietkau <nbd@xxxxxxxx>
Signed-off-by: Alexander Duyck <alexanderduyck@xxxxxx>
---
 net/core/gro.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/core/gro.c b/net/core/gro.c
index 506f83d715f8..4bac7ea6e025 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -162,6 +162,15 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
 	struct sk_buff *lp;
 	int segs;
 
+	/* Do not splice page pool based packets w/ non-page pool
+	 * packets. This can result in reference count issues as page
+	 * pool pages will not decrement the reference count and will
+	 * instead be immediately returned to the pool or have frag
+	 * count decremented.
+	 */
+	if (p->pp_recycle != skb->pp_recycle)
+		return -ETOOMANYREFS;
+
 	/* pairs with WRITE_ONCE() in netif_set_gro_max_size() */
 	gro_max_size = READ_ONCE(p->dev->gro_max_size);