netdev - Re: [PATCH v1 net 3/3] af_unix: Prepare MSG

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Message-ID: <bef45d8e-35b7-42e4-bf6c-768da5b6d8f2@oracle.com>
Date: Tue, 9 Apr 2024 17:09:24 -0700
From: Rao Shoaib <rao.shoaib@...cle.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc: Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net 3/3] af_unix: Prepare MSG_OOB deprecation.

This feature was added because it was needed by Oracle products. The 
bugs found are corner cases and happen with new feature, at the time all 
tests passed. If you do not feel like fixing these bugs that is fine, 
let me know and I will address them, but removing the feature completely 
should not be an option.

Plus Amazon has it's own closed/proprietary distribution. If this is an 
issue please configure your repo to not include this feature. Many 
distributions choose not to include several features.

Shoaib

On 4/9/24 15:52, Kuniyuki Iwashima wrote:
> Commit 314001f0bf92 ("af_unix: Add OOB support") introduced MSG_OOB
> support for AF_UNIX, and it's about 3 years ago.  Since then, MSG_OOB
> is the playground for syzbot.
> 
> MSG_OOB support is guarded with CONFIG_AF_UNIX_OOB, but it's enabled
> by default and cannot be disabled without editing .config manually
> because of the lack of prompt.
> 
> We recently found 3 wrong behaviours with basic functionality that
> no one have noticed for 3 years, so it seems there is no real user
> and even the author is not using OOB feature.  [0]
> 
> This is a good opportunity to drop MSG_OOB support.
> 
> Let's switch the default config to n and add warning so that someone
> using MSG_OOB in a real workload can notice it before MSG_OOB support
> is removed completely.
> 
> Link: https://urldefense.com/v3/__https://lore.kernel.org/netdev/472044aa-4427-40f0-9b9a-bce75d5c8aac@oracle.com/__;!!ACWV5N9M2RV99hQ!M7skvfZ7iV_Wz5V4lcoDCSabTe02sk-cpFNYB5WNcgszkzbp3hHoasDagxKSqLdcBtgZ_ckaf5-RBE4$  [0]
> Fixes: 314001f0bf92 ("af_unix: Add OOB support")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
> Added Fixes tag so that it can be backported to corresponding stable
> kernels.
> ---
>   net/unix/Kconfig   | 4 ++--
>   net/unix/af_unix.c | 2 ++
>   2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/unix/Kconfig b/net/unix/Kconfig
> index 8b5d04210d7c..9d9270fdc1fe 100644
> --- a/net/unix/Kconfig
> +++ b/net/unix/Kconfig
> @@ -17,9 +17,9 @@ config UNIX
>   	  Say Y unless you know what you are doing.
>   
>   config	AF_UNIX_OOB
> -	bool
> +	bool "Unix MSG_OOB support"
>   	depends on UNIX
> -	default y
> +	default n
>   
>   config UNIX_DIAG
>   	tristate "UNIX: socket monitoring interface"
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 9a6ad5974dff..fecca27aa77f 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2253,6 +2253,8 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
>   	err = -EOPNOTSUPP;
>   	if (msg->msg_flags & MSG_OOB) {
>   #if IS_ENABLED(CONFIG_AF_UNIX_OOB)
> +		pr_warn_once("MSG_OOB support will be removed in 2025.\n");
> +
>   		if (len)
>   			len--;
>   		else