linux-kernel - Re: [PATCH net-next] netlink: Fix potential skb memleak in netlink

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Message-ID: <a0084580-7956-0825-42de-90c0b220cc21@linux.alibaba.com>
Date:   Fri, 4 Nov 2022 14:15:39 +0800
From:   Tao Chen <chentao.kernel@...ux.alibaba.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Johannes Berg <johannes@...solutions.net>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Petr Machata <petrm@...dia.com>,
        Kees Cook <keescook@...omium.org>,
        Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] netlink: Fix potential skb memleak in
 netlink_ack

在 2022/11/3 上午5:39, Jakub Kicinski 写道:
> On Wed,  2 Nov 2022 20:08:20 +0800 Tao Chen wrote:
>> We should clean the skb resource if nlmsg_put/append failed
>> , so fix it.
> 
> The comma should be at the end of the previous line.
> But really the entire ", so fix it." is redundant.
> 
Thank you, i will pay attention next time
>> Fiexs: commit 738136a0e375 ("netlink: split up copies in the
>> ack construction")
> 
> Please look around to see how to correctly format a Fixes tag
> (including not line wrapping it).
> 
> How did you find this bug? An automated tool? Syzbot?
> 
> One more note below on the code itself.
> 
This was found by the coverity tool, i will add it.
>> Signed-off-by: Tao Chen <chentao.kernel@...ux.alibaba.com>
>> ---
>>   net/netlink/af_netlink.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
>> index c6b8207e..9d73dae 100644
>> --- a/net/netlink/af_netlink.c
>> +++ b/net/netlink/af_netlink.c
>> @@ -2500,7 +2500,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
>>   
>>   	skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
>>   	if (!skb)
>> -		goto err_bad_put;
>> +		goto err_skb;
>>   
>>   	rep = nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
>>   			NLMSG_ERROR, sizeof(*errmsg), flags);
>> @@ -2528,6 +2528,8 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
>>   	return;
>>   
>>   err_bad_put:
>> +	kfree_skb(skb);
> 
> Please use nlmsg_free() since we allocated with nlmsg_new().
> 
Ok, i will send it in v2.
>> +err_skb:
>>   	NETLINK_CB(in_skb).sk->sk_err = ENOBUFS;
>>   	sk_error_report(NETLINK_CB(in_skb).sk);
>>   }