netdev - Re: [PATCH net,v5,2/2] net/smc: modify smc

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Message-ID: <e0f35083-7604-4766-990a-f77554e0202f@redhat.com>
Date: Tue, 20 Aug 2024 12:45:00 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Jeongjun Park <aha310510@...il.com>, wenjia@...ux.ibm.com,
 jaka@...ux.ibm.com, alibuda@...ux.alibaba.com, tonylu@...ux.alibaba.com,
 guwen@...ux.alibaba.com
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 dust.li@...ux.alibaba.com, ubraun@...ux.vnet.ibm.com, utz.bacher@...ibm.com,
 linux-s390@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net,v5,2/2] net/smc: modify smc_sock structure



On 8/15/24 06:39, Jeongjun Park wrote:
> 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 modify the smc_sock structure.
> 
> Fixes: ac7138746e14 ("smc: establish new socket family")
> Signed-off-by: Jeongjun Park <aha310510@...il.com>
> ---
>   net/smc/smc.h | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/smc/smc.h b/net/smc/smc.h
> index 34b781e463c4..0d67a02a6ab1 100644
> --- a/net/smc/smc.h
> +++ b/net/smc/smc.h
> @@ -283,7 +283,10 @@ struct smc_connection {
>   };
>   
>   struct smc_sock {				/* smc sock container */
> -	struct sock		sk;
> +	union {
> +		struct sock		sk;
> +		struct inet_sock	inet;
> +	};
>   	struct socket		*clcsock;	/* internal tcp socket */
>   	void			(*clcsk_state_change)(struct sock *sk);
>   						/* original stat_change fct. */

As per the running discussion here:

https://lore.kernel.org/all/5ad4de6f-48d4-4d1b-b062-e1cd2e8b3600@linux.ibm.com/#t

you should include at least a add a comment to the union, describing 
which one is used in which case.

My personal preference would be directly replacing 'struct sk' with
'struct inet_sock inet;' and adjust all the smc->sk access accordingly, 
likely via a new helper.

I understand that would be much more invasive, but would align with 
other AF.

Thanks,

Paolo