mac80211: fix a page refcounting issue leading to leaks/crashes in rx A-MSDU decap

Signed-off-by: Felix Fietkau <nbd@nbd.name>
(cherry-picked from commit 9501469e1146c6d76b7dde6391479314897ba4d8)

diff --git a/package/kernel/mac80211/patches/subsys/370-cfg80211-fix-page-refcount-issue-in-A-MSDU-decap.patch b/package/kernel/mac80211/patches/subsys/370-cfg80211-fix-page-refcount-issue-in-A-MSDU-decap.patch
new file mode 100644 (file)
index 0000000..9dba580
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/370-cfg80211-fix-page-refcount-issue-in-A-MSDU-decap.patch
@@ -0,0 +1,25 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Mon, 13 Jan 2020 18:34:31 +0100
+Subject: [PATCH] cfg80211: fix page refcount issue in A-MSDU decap
+
+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>
+---
+
+--- a/net/wireless/util.c
++++ b/net/wireless/util.c
+@@ -537,7 +537,7 @@ __frame_add_frag(struct sk_buff *skb, st
+       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);
+ }