linux-kernel - Re: [PATCH net] ipv6: addrlabel: fix possible memory leak in ip6addrlbl_net

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Date:   Tue, 24 Nov 2020 15:19:46 +0800
From:   "wanghai (M)" <wanghai38@...wei.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     <davem@...emloft.net>, <kuznet@....inr.ac.ru>,
        <yoshfuji@...ux-ipv6.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] ipv6: addrlabel: fix possible memory leak in
 ip6addrlbl_net_init


在 2020/11/24 9:22, Jakub Kicinski 写道:
> On Sun, 22 Nov 2020 10:34:56 +0800 Wang Hai wrote:
>> kmemleak report a memory leak as follows:
>>
>> unreferenced object 0xffff8880059c6a00 (size 64):
>>    comm "ip", pid 23696, jiffies 4296590183 (age 1755.384s)
>>    hex dump (first 32 bytes):
>>      20 01 00 10 00 00 00 00 00 00 00 00 00 00 00 00   ...............
>>      1c 00 00 00 00 00 00 00 00 00 00 00 07 00 00 00  ................
>>    backtrace:
>>      [<00000000aa4e7a87>] ip6addrlbl_add+0x90/0xbb0
>>      [<0000000070b8d7f1>] ip6addrlbl_net_init+0x109/0x170
>>      [<000000006a9ca9d4>] ops_init+0xa8/0x3c0
>>      [<000000002da57bf2>] setup_net+0x2de/0x7e0
>>      [<000000004e52d573>] copy_net_ns+0x27d/0x530
>>      [<00000000b07ae2b4>] create_new_namespaces+0x382/0xa30
>>      [<000000003b76d36f>] unshare_nsproxy_namespaces+0xa1/0x1d0
>>      [<0000000030653721>] ksys_unshare+0x3a4/0x780
>>      [<0000000007e82e40>] __x64_sys_unshare+0x2d/0x40
>>      [<0000000031a10c08>] do_syscall_64+0x33/0x40
>>      [<0000000099df30e7>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>
>> We should free all rules when we catch an error in ip6addrlbl_net_init().
>> otherwise a memory leak will occur.
>>
>> Fixes: 2a8cc6c89039 ("[IPV6] ADDRCONF: Support RFC3484 configurable address selection policy table.")
>> Reported-by: Hulk Robot <hulkci@...wei.com>
>> Signed-off-by: Wang Hai <wanghai38@...wei.com>
> We can simplify this function.
>
>> diff --git a/net/ipv6/addrlabel.c b/net/ipv6/addrlabel.c
>> index 642fc6ac13d2..637e323a0224 100644
>> --- a/net/ipv6/addrlabel.c
>> +++ b/net/ipv6/addrlabel.c
>> @@ -306,6 +306,8 @@ static int ip6addrlbl_del(struct net *net,
>>   /* add default label */
>>   static int __net_init ip6addrlbl_net_init(struct net *net)
>>   {
>> +	struct ip6addrlbl_entry *p = NULL;
>> +	struct hlist_node *n;
>>   	int err = 0;
> err does not need init
>
>>   	int i;
>>   
>> @@ -320,9 +322,17 @@ static int __net_init ip6addrlbl_net_init(struct net *net)
> instead of the temporary ret variable we can assign directly to err
>
>>   					 ip6addrlbl_init_table[i].prefixlen,
>>   					 0,
>>   					 ip6addrlbl_init_table[i].label, 0);
>> -		/* XXX: should we free all rules when we catch an error? */
>> -		if (ret && (!err || err != -ENOMEM))
>> +		if (ret && (!err || err != -ENOMEM)) {
> this will become if (err)
>
>>   			err = ret;
>> +			goto err_ip6addrlbl_add;
>> +		}
>> +	}
>> +	return err;
> return 0;
>
>> +err_ip6addrlbl_add:
>> +	hlist_for_each_entry_safe(p, n, &net->ipv6.ip6addrlbl_table.head, list) {
>> +		hlist_del_rcu(&p->list);
>> +		kfree_rcu(p, rcu);
>>   	}
>>   	return err;
>>   }

Thanks for advice. I just sent a v2

“[PATCH net v2] ipv6: addrlabel: fix possible memory leak in 
ip6addrlbl_net_init”

> .
>