linux-kernel - Re: [PATCH net] net/smc: prevent NULL pointer dereference in txopt

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Message-ID: <4ccf34a0-3db2-4cbf-a9b2-cf585af8c63a@linux.alibaba.com>
Date: Tue, 13 Aug 2024 16:52:16 +0800
From: "D. Wythe" <alibuda@...ux.alibaba.com>
To: Gerd Bayer <gbayer@...ux.ibm.com>, Jeongjun Park <aha310510@...il.com>,
 wenjia@...ux.ibm.com, jaka@...ux.ibm.com
Cc: tonylu@...ux.alibaba.com, guwen@...ux.alibaba.com, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 dust.li@...ux.alibaba.com, linux-s390@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net/smc: prevent NULL pointer dereference in
 txopt_get



On 8/13/24 4:05 PM, Gerd Bayer wrote:
> On Sun, 2024-08-11 at 02:22 +0900, Jeongjun Park wrote:
>> Since smc_inet6_prot does not initialize ipv6_pinfo_offset,
>> inet6_create() copies an incorrect address value, sk + 0 (offset), to
>> inet_sk(sk)->pinet6.
>>
>> In addition, since inet_sk(sk)->pinet6 and smc_sk(sk)->clcsock
>> practically point to the same address, when smc_create_clcsk() stores
>> the newly created clcsock in smc_sk(sk)->clcsock, inet_sk(sk)->pinet6
>> is corrupted into clcsock. This causes NULL pointer dereference and
>> various other memory corruptions.
>>
>> To solve this, we need to add a smc6_sock structure for
>> ipv6_pinfo_offset initialization and modify the smc_sock structure.
> I can not argue substantially with that... There's very little IPv6
> testing that I'm aware of. But do you really need to move that much
> code around and change whitespace for you fix?
>
> [--- snip ---]
>
>
>> Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
>> Signed-off-by: Jeongjun Park <aha310510@...il.com>
>> ---
>>   net/smc/smc.h      | 19 ++++++++++---------
>>   net/smc/smc_inet.c | 24 +++++++++++++++---------
>>   2 files changed, 25 insertions(+), 18 deletions(-)
>>
>> diff --git a/net/smc/smc.h b/net/smc/smc.h
>> index 34b781e463c4..f4d9338b5ed5 100644
>> --- a/net/smc/smc.h
>> +++ b/net/smc/smc.h
>> @@ -284,15 +284,6 @@ struct smc_connection {
>>   
>>   struct smc_sock {				/* smc sock
>> container */
>>   	struct sock		sk;
>> -	struct socket		*clcsock;	/* internal tcp
>> socket */
>> -	void			(*clcsk_state_change)(struct sock
>> *sk);
>> -						/* original
>> stat_change fct. */
>> -	void			(*clcsk_data_ready)(struct sock
>> *sk);
>> -						/* original
>> data_ready fct. */
>> -	void			(*clcsk_write_space)(struct sock
>> *sk);
>> -						/* original
>> write_space fct. */
>> -	void			(*clcsk_error_report)(struct sock
>> *sk);
>> -						/* original
>> error_report fct. */
>>   	struct smc_connection	conn;		/* smc connection */
>>   	struct smc_sock		*listen_smc;	/* listen
>> parent */
>>   	struct work_struct	connect_work;	/* handle non-
>> blocking connect*/
>> @@ -325,6 +316,16 @@ struct smc_sock {				/*
>> smc sock container */
>>   						/* protects clcsock
>> of a listen
>>   						 * socket
>>   						 * */
>> +	struct socket		*clcsock;	/* internal tcp
>> socket */
>> +	void			(*clcsk_state_change)(struct sock
>> *sk);
>> +						/* original
>> stat_change fct. */
>> +	void			(*clcsk_data_ready)(struct sock
>> *sk);
>> +						/* original
>> data_ready fct. */
>> +	void			(*clcsk_write_space)(struct sock
>> *sk);
>> +						/* original
>> write_space fct. */
>> +	void			(*clcsk_error_report)(struct sock
>> *sk);
>> +						/* original
>> error_report fct. */
>> +
>>   };

Hi Jeongjun,

I have no problem with this fix, thank you for your assistance.
But, what this here was for ?


>>   
>>   #define smc_sk(ptr) container_of_const(ptr, struct smc_sock, sk)
>> diff --git a/net/smc/smc_inet.c b/net/smc/smc_inet.c
>> index bece346dd8e9..3c54faef6042 100644
>> --- a/net/smc/smc_inet.c
>> +++ b/net/smc/smc_inet.c
>> @@ -60,16 +60,22 @@ static struct inet_protosw smc_inet_protosw = {
>>   };
>>   
>>   #if IS_ENABLED(CONFIG_IPV6)
>> +struct smc6_sock {
>> +	struct smc_sock smc;
>> +	struct ipv6_pinfo np;
>> +};
>> +
>>   static struct proto smc_inet6_prot = {
>> -	.name		= "INET6_SMC",
>> -	.owner		= THIS_MODULE,
>> -	.init		= smc_inet_init_sock,
>> -	.hash		= smc_hash_sk,
>> -	.unhash		= smc_unhash_sk,
>> -	.release_cb	= smc_release_cb,
>> -	.obj_size	= sizeof(struct smc_sock),
>> -	.h.smc_hash	= &smc_v6_hashinfo,
>> -	.slab_flags	= SLAB_TYPESAFE_BY_RCU,
>> +	.name		       = "INET6_SMC",
>> +	.owner		       = THIS_MODULE,
>> +	.init		       = smc_inet_init_sock,
>> +	.hash		       = smc_hash_sk,
>> +	.unhash		       = smc_unhash_sk,
>> +	.release_cb	       = smc_release_cb,
>> +	.obj_size	       = sizeof(struct smc6_sock),
>> +	.h.smc_hash	       = &smc_v6_hashinfo,
>> +	.slab_flags	       = SLAB_TYPESAFE_BY_RCU,
>> +	.ipv6_pinfo_offset = offsetof(struct smc6_sock, np),

Since you have done alignment, why not align the  '='.

> The line above together with the definition of struct smc6_sock seem to
> be the only changes relevant to fixing the issue, IMHO.
>
>>   };
>>   
>>   static const struct proto_ops smc_inet6_stream_ops = {
>> --
>>
> Thanks, Gerd