netdev - Re: [PATCH net-next] scm: add user copy checks to put

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Date:   Fri, 17 Feb 2023 17:41:21 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        eric.dumazet@...il.com
Subject: Re: [PATCH net-next] scm: add user copy checks to put_cmsg()

On Fri, Feb 17, 2023 at 06:24:54PM +0000, Eric Dumazet wrote:
> This is a followup of commit 2558b8039d05 ("net: use a bounce
> buffer for copying skb->mark")
> 
> x86 and powerpc define user_access_begin, meaning
> that they are not able to perform user copy checks
> when using user_write_access_begin() / unsafe_copy_to_user()
> and friends [1]
> 
> Instead of waiting bugs to trigger on other arches,
> add a check_object_size() in put_cmsg() to make sure
> that new code tested on x86 with CONFIG_HARDENED_USERCOPY=y
> will perform more security checks.
> 
> [1] We can not generically call check_object_size() from
> unsafe_copy_to_user() because UACCESS is enabled at this point.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Thanks!

Acked-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook