From 81c044fc3bdc5b7be967cd3682528ea94b58c06a Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Mon, 13 Jan 2020 19:21:07 +0100
Subject: [PATCH] cfg80211: fix page refcount issue in A-MSDU decap
Git-commit: 81c044fc3bdc5b7be967cd3682528ea94b58c06a
Patch-mainline: v5.5-rc7
References: bsc#1051510

The fragments attached to a skb can be part of a compound page. In that case,
page_ref_inc will increment the refcount for the wrong page. Fix this by
using get_page instead, which calls page_ref_inc on the compound head and
also checks for overflow.

Fixes: 2b67f944f88c ("cfg80211: reuse existing page fragments in A-MSDU rx")
Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20200113182107.20461-1-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/wireless/util.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 5b4ed5bbc542..8481e9ac33da 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -564,7 +564,7 @@ __frame_add_frag(struct sk_buff *skb, struct page *page,
 	struct skb_shared_info *sh = skb_shinfo(skb);
 	int page_offset;
 
-	page_ref_inc(page);
+	get_page(page);
 	page_offset = ptr - page_address(page);
 	skb_add_rx_frag(skb, sh->nr_frags, page, page_offset, len, size);
 }
-- 
2.16.4