When skb_zerocopy() copies devmem payload fragments, it fails to update
the target skb's unreadable flag. This causes the target to appear as
readable memory.

Propagate the unreadable flag if any devmem fragments were copied from
the source.

Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags")
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Bobby Eshleman <bobbyeshleman@gmail.com>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Mina Almasry <almasrymina@google.com>
---
 net/core/skbuff.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ba3dbac80fb49..aebe8ea74776a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3928,6 +3928,9 @@ skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
 	}
 	skb_shinfo(to)->nr_frags = j;
 
+	if (i > 0 && from->unreadable)
+		to->unreadable = 1;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(skb_zerocopy);
-- 
2.55.0.571.g244d577d93-goog