From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xie He Subject: [PATCH v2] drivers/net/wan/lapbether: Fixed the value of hard_header_len Date: Sun, 5 Jul 2020 17:45:21 -0700 Message-ID: <20200706004521.78091-1-xie.he.0141@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:subject:date:message-id:mime-version :content-transfer-encoding; bh=4OaY8bZwpJuqmoIiivxLlaUVMaXxlk23RnTZnLFJFaY=; b=kd2w6hJIZW9PFP0lMor0Df7aUbziEFd/nGD0zMJOBuuWd21lAfqEipSBJb29CnzV6O 0IrRM13BFz+vsC6/9Zykj4l47i8zCsw6O9fnI24mxY9GAQKldLqnA/sqOBX9zfVTTLoX +1s//whclybYcTOEZL22qwzGJNLYXnxCXcO7MSRysvfNpZj8/sMQRnMVXynCW99vpeo4 rid4eAngZ438yS4XzZlqtwOg24OmCqeVkg4rbOuqt8LUpDUEEetfvGlzCocBqDBGzkVH kqSW5OdhEIKTLzddRU25moBgkZwDhh0PSHDyKHRAI9ih5RnuJbWyc2bQ0IC9nQk197dW zqIA== Sender: netdev-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: "David S. Miller" , Jakub Kicinski , Madhuparna Bhowmik , Xie He , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-x25@vger.kernel.org When this driver transmits data, first this driver will remove a pseudo header of 1 byte, then the lapb module will prepend the LAPB header of 2 or 3 bytes, then this driver will prepend a length field of 2 bytes, then the underlying Ethernet device will prepend its own header. So, the header length required should be: -1 + 3 + 2 + "the header length needed by the underlying device". This patch fixes kernel panic when this driver is used with AF_PACKET SOCK_DGRAM sockets. Signed-off-by: Xie He --- Change in v2: added a comment in the code drivers/net/wan/lapbether.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c index e30d91a38cfb..284832314f31 100644 --- a/drivers/net/wan/lapbether.c +++ b/drivers/net/wan/lapbether.c @@ -303,7 +303,6 @@ static void lapbeth_setup(struct net_device *dev) dev->netdev_ops = &lapbeth_netdev_ops; dev->needs_free_netdev = true; dev->type = ARPHRD_X25; - dev->hard_header_len = 3; dev->mtu = 1000; dev->addr_len = 0; } @@ -324,6 +323,14 @@ static int lapbeth_new_device(struct net_device *dev) if (!ndev) goto out; + /* When transmitting data: + * first this driver removes a pseudo header of 1 byte, + * then the lapb module prepends an LAPB header of at most 3 bytes, + * then this driver prepends a length field of 2 bytes, + * then the underlying Ethernet device prepends its own header. + */ + ndev->hard_header_len = -1 + 3 + 2 + dev->hard_header_len; + lapbeth = netdev_priv(ndev); lapbeth->axdev = ndev; -- 2.25.1