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Subject: Re: [PATCH] tipc: compat: allow tipc commands without arguments
To:     Taras Kondratiuk <takondra@cisco.com>,
        Jon Maloy <jon.maloy@ericsson.com>,
        "David S. Miller" <davem@davemloft.net>
CC:     <netdev@vger.kernel.org>, <tipc-discussion@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <xe-linux-external@cisco.com>,
        <stable@vger.kernel.org>
References: <20190729221507.48893-1-takondra@cisco.com>
From:   Ying Xue <ying.xue@windriver.com>
Message-ID: <605b6a6e-8bdd-c95f-ac00-9dd895fcc6a3@windriver.com>
Date:   Thu, 1 Aug 2019 21:12:36 +0800
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On 7/30/19 6:15 AM, Taras Kondratiuk wrote:
> Commit 2753ca5d9009 ("tipc: fix uninit-value in tipc_nl_compat_doit")
> broke older tipc tools that use compat interface (e.g. tipc-config from
> tipcutils package):
> 
> % tipc-config -p
> operation not supported
> 
> The commit started to reject TIPC netlink compat messages that do not
> have attributes. It is too restrictive because some of such messages are
> valid (they don't need any arguments):
> 
> % grep 'tx none' include/uapi/linux/tipc_config.h
> #define  TIPC_CMD_NOOP              0x0000    /* tx none, rx none */
> #define  TIPC_CMD_GET_MEDIA_NAMES   0x0002    /* tx none, rx media_name(s) */
> #define  TIPC_CMD_GET_BEARER_NAMES  0x0003    /* tx none, rx bearer_name(s) */
> #define  TIPC_CMD_SHOW_PORTS        0x0006    /* tx none, rx ultra_string */
> #define  TIPC_CMD_GET_REMOTE_MNG    0x4003    /* tx none, rx unsigned */
> #define  TIPC_CMD_GET_MAX_PORTS     0x4004    /* tx none, rx unsigned */
> #define  TIPC_CMD_GET_NETID         0x400B    /* tx none, rx unsigned */
> #define  TIPC_CMD_NOT_NET_ADMIN     0xC001    /* tx none, rx none */
> 
> This patch relaxes the original fix and rejects messages without
> arguments only if such arguments are expected by a command (reg_type is
> non zero).
> 
> Fixes: 2753ca5d9009 ("tipc: fix uninit-value in tipc_nl_compat_doit")
> Cc: stable@vger.kernel.org
> Signed-off-by: Taras Kondratiuk <takondra@cisco.com>

Acked-by: Ying Xue <ying.xue@windriver.com>

> ---
> The patch is based on v5.3-rc2.
> 
>  net/tipc/netlink_compat.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c
> index d86030ef1232..e135d4e11231 100644
> --- a/net/tipc/netlink_compat.c
> +++ b/net/tipc/netlink_compat.c
> @@ -55,6 +55,7 @@ struct tipc_nl_compat_msg {
>  	int rep_type;
>  	int rep_size;
>  	int req_type;
> +	int req_size;
>  	struct net *net;
>  	struct sk_buff *rep;
>  	struct tlv_desc *req;
> @@ -257,7 +258,8 @@ static int tipc_nl_compat_dumpit(struct tipc_nl_compat_cmd_dump *cmd,
>  	int err;
>  	struct sk_buff *arg;
>  
> -	if (msg->req_type && !TLV_CHECK_TYPE(msg->req, msg->req_type))
> +	if (msg->req_type && (!msg->req_size ||
> +			      !TLV_CHECK_TYPE(msg->req, msg->req_type)))
>  		return -EINVAL;
>  
>  	msg->rep = tipc_tlv_alloc(msg->rep_size);
> @@ -354,7 +356,8 @@ static int tipc_nl_compat_doit(struct tipc_nl_compat_cmd_doit *cmd,
>  {
>  	int err;
>  
> -	if (msg->req_type && !TLV_CHECK_TYPE(msg->req, msg->req_type))
> +	if (msg->req_type && (!msg->req_size ||
> +			      !TLV_CHECK_TYPE(msg->req, msg->req_type)))
>  		return -EINVAL;
>  
>  	err = __tipc_nl_compat_doit(cmd, msg);
> @@ -1278,8 +1281,8 @@ static int tipc_nl_compat_recv(struct sk_buff *skb, struct genl_info *info)
>  		goto send;
>  	}
>  
> -	len = nlmsg_attrlen(req_nlh, GENL_HDRLEN + TIPC_GENL_HDRLEN);
> -	if (!len || !TLV_OK(msg.req, len)) {
> +	msg.req_size = nlmsg_attrlen(req_nlh, GENL_HDRLEN + TIPC_GENL_HDRLEN);
> +	if (msg.req_size && !TLV_OK(msg.req, msg.req_size)) {
>  		msg.rep = tipc_get_err_tlv(TIPC_CFG_NOT_SUPPORTED);
>  		err = -EOPNOTSUPP;
>  		goto send;
>