netdev - Re: [PATCH iproute2 v3] ipnetns: use-after-free problem in get_netnsid_from

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Message-ID: <a7e88fd6-65be-97f9-f660-152fabef565e@huawei.com>
Date:   Sun, 5 May 2019 09:15:58 +0800
From:   Zhiqiang Liu <liuzhiqiang26@...wei.com>
To:     David Ahern <dsahern@...il.com>, <stephen@...workplumber.org>,
        <liuhangbin@...il.com>, <kuznet@....inr.ac.ru>
CC:     <nicolas.dichtel@...nd.com>, <phil@....cc>,
        "wangxiaogang (F)" <wangxiaogang3@...wei.com>,
        Mingfangsen <mingfangsen@...wei.com>,
        "Zhoukang (A)" <zhoukang7@...wei.com>, <kouhuiying@...wei.com>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH iproute2 v3] ipnetns: use-after-free problem in
 get_netnsid_from_name func

> On 5/4/19 1:26 AM, Zhiqiang Liu wrote:
>>
>> diff --git a/ip/ipnetns.c b/ip/ipnetns.c
>> index 430d884..d72be95 100644
>> --- a/ip/ipnetns.c
>> +++ b/ip/ipnetns.c
>> @@ -107,7 +107,7 @@ int get_netnsid_from_name(const char *name)
>>  	struct nlmsghdr *answer;
>>  	struct rtattr *tb[NETNSA_MAX + 1];
>>  	struct rtgenmsg *rthdr;
>> -	int len, fd;
>> +	int len, fd, ret = -1;
>>
>>  	netns_nsid_socket_init();
>>
>> @@ -134,8 +134,9 @@ int get_netnsid_from_name(const char *name)
>>  	parse_rtattr(tb, NETNSA_MAX, NETNS_RTA(rthdr), len);
>>
>>  	if (tb[NETNSA_NSID]) {
>> +		ret = rta_getattr_u32(tb[NETNSA_NSID]);
>>  		free(answer);
>> -		return rta_getattr_u32(tb[NETNSA_NSID]);
>> +		return ret;
> 
> set ret here, drop the free, let it proceed down to the existing free
> and return but now using ret. That way there is 1 exit path and handles
> the cleanup

Yes, you are right. I will do that in the v4 patch.
That is very nice of you. Thanks a lot.