linux-kernel - Re: [PATCH net] xfrm: Fix ignored return value in xfrm6

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Message-ID: <917fab11-ae57-07b9-ae67-7c290c7c6723@huawei.com>
Date:   Mon, 7 Nov 2022 11:22:40 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <steffen.klassert@...unet.com>, <herbert@...dor.apana.org.au>,
        <davem@...emloft.net>, <yoshfuji@...ux-ipv6.org>,
        <dsahern@...nel.org>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <mkubecek@...e.cz>
Subject: Re: [PATCH net] xfrm: Fix ignored return value in xfrm6_init()

Hi,

On 2022/11/7 3:08, Leon Romanovsky wrote:
> On Thu, Nov 03, 2022 at 05:07:13PM +0800, Chen Zhongjin wrote:
>> When IPv6 module initializing in xfrm6_init(), register_pernet_subsys()
>> is possible to fail but its return value is ignored.
>>
>> If IPv6 initialization fails later and xfrm6_fini() is called,
>> removing uninitialized list in xfrm6_net_ops will cause null-ptr-deref:
>>
>> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
>> CPU: 1 PID: 330 Comm: insmod
>> RIP: 0010:unregister_pernet_operations+0xc9/0x450
>> Call Trace:
>>   <TASK>
>>   unregister_pernet_subsys+0x31/0x3e
>>   xfrm6_fini+0x16/0x30 [ipv6]
>>   ip6_route_init+0xcd/0x128 [ipv6]
>>   inet6_init+0x29c/0x602 [ipv6]
>>   ...
>>
>> Fix it by catching the error return value of register_pernet_subsys().
>>
>> Fixes: 8d068875caca ("xfrm: make gc_thresh configurable in all namespaces")
>> Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
>> ---
>>   net/ipv6/xfrm6_policy.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
> I see same error in net/ipv4/xfrm4_policy.c which introduced by same
> commit mentioned in Fixes line.

It's true that in xfrm4_init() the ops->init is possible to fail as well.

However there is no error handling or exit path for ipv4, so IIUC the 
ops won't be unregistered anyway.

Considering that ipv4 don't handle most of error in initialization, 
maybe it's better to keep it as it is?


Best,

Chen

> Thanks
>