linux-kernel - [PATCH 4.4 53/93] batman-adv: Avoid nullptr dereference in bla after vlan_insert

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Date:   Thu, 19 Mar 2020 13:59:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sven Eckelmann <sven@...fation.org>,
        Marek Lindner <mareklindner@...mailbox.ch>,
        Simon Wunderlich <sw@...onwunderlich.de>
Subject: [PATCH 4.4 53/93] batman-adv: Avoid nullptr dereference in bla after vlan_insert_tag

From: Sven Eckelmann <sven@...fation.org>

commit 10c78f5854d361ded4736c1831948e0a5f67b932 upstream.

vlan_insert_tag can return NULL on errors. The bridge loop avoidance code
therefore has to check the return value of vlan_insert_tag for NULL before
it can safely operate on this pointer.

Fixes: 23721387c409 ("batman-adv: add basic bridge loop avoidance code")
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Marek Lindner <mareklindner@...mailbox.ch>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/batman-adv/bridge_loop_avoidance.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -352,9 +352,12 @@ static void batadv_bla_send_claim(struct
 		break;
 	}
 
-	if (vid & BATADV_VLAN_HAS_TAG)
+	if (vid & BATADV_VLAN_HAS_TAG) {
 		skb = vlan_insert_tag(skb, htons(ETH_P_8021Q),
 				      vid & VLAN_VID_MASK);
+		if (!skb)
+			goto out;
+	}
 
 	skb_reset_mac_header(skb);
 	skb->protocol = eth_type_trans(skb, soft_iface);