From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59BD71C31 for ; Wed, 23 Nov 2022 09:57:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C2397C433D6; Wed, 23 Nov 2022 09:57:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669197458; bh=rxD+kNMxCUOMAYgE0xEan8kZoKIajeVAmFMKv1OXqlo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QdxvnedWArkObKkwTF6QB2Bm6ev8cYfqqISOMbDei+ufFRQpQhcBUplfEFGbqiNN+ sG1ZwZ7Q3sRR7iycikRJ7JW804NmelUDZDNpvv6HUZ9cTkc2vFkfJBpx0LzRJxTT4g dLD2x2valxbX5QMAcLSQR68TbHO+ofqdCH1jZ+cI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Eric Dumazet , "David S. Miller" Subject: [PATCH 6.0 298/314] macvlan: enforce a consistent minimal mtu Date: Wed, 23 Nov 2022 09:52:23 +0100 Message-Id: <20221123084639.046672896@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084625.457073469@linuxfoundation.org> References: <20221123084625.457073469@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Eric Dumazet commit b64085b00044bdf3cd1c9825e9ef5b2e0feae91a upstream. macvlan should enforce a minimal mtu of 68, even at link creation. This patch avoids the current behavior (which could lead to crashes in ipv6 stack if the link is brought up) $ ip link add macvlan1 link eno1 mtu 8 type macvlan # This should fail ! $ ip link sh dev macvlan1 5: macvlan1@eno1: mtu 8 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether 02:47:6c:24:74:82 brd ff:ff:ff:ff:ff:ff $ ip link set macvlan1 mtu 67 Error: mtu less than device minimum. $ ip link set macvlan1 mtu 68 $ ip link set macvlan1 mtu 8 Error: mtu less than device minimum. Fixes: 91572088e3fd ("net: use core MTU range checking in core net infra") Reported-by: syzbot Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/macvlan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/net/macvlan.c +++ b/drivers/net/macvlan.c @@ -1192,7 +1192,7 @@ void macvlan_common_setup(struct net_dev { ether_setup(dev); - dev->min_mtu = 0; + /* ether_setup() has set dev->min_mtu to ETH_MIN_MTU. */ dev->max_mtu = ETH_MAX_MTU; dev->priv_flags &= ~IFF_TX_SKB_SHARING; netif_keep_dst(dev);