[SRU Bionic PATCH 1/1] mac80211: fix memory corruption in EAPOL handling

Stefan Bader stefan.bader at canonical.com
Wed Jul 28 14:36:38 UTC 2021

From: Davis Mosenkovs <davis at mosenkovs.lv>

BugLink: https://bugs.launchpad.net/bugs/1938013

Commit e3d4030498c3 ("mac80211: do not accept/forward invalid EAPOL
frames") uses skb_mac_header() before eth_type_trans() is called
leading to incorrect pointer, the pointer gets written to. This issue
has appeared during backporting to 4.4, 4.9 and 4.14.

Fixes: e3d4030498c3 ("mac80211: do not accept/forward invalid EAPOL frames")
Link: https://lore.kernel.org/r/CAHQn7pKcyC_jYmGyTcPCdk9xxATwW5QPNph=bsZV8d-HPwNsyA@mail.gmail.com
Cc: <stable at vger.kernel.org> # 4.4.x
Signed-off-by: Davis Mosenkovs <davis at mosenkovs.lv>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

(cherry picked from commit 3b6d3d1884fa31f701603772732c404020b0598d linux.4.14.y)
Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
Tested-by: Juerg Haefliger <juerg.haefliger at canonical.com>
 net/mac80211/rx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 95e6d41626d6..7847b168c9ce 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2407,7 +2407,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 	if (skb) {
-		struct ethhdr *ehdr = (void *)skb_mac_header(skb);
+		struct ethhdr *ehdr = (struct ethhdr *)skb->data;
 		/* deliver to local stack */
 		skb->protocol = eth_type_trans(skb, dev);

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