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Date:   Fri, 20 Nov 2020 09:35:59 -0600
From:   Tyler Hicks <code@tyhicks.com>
To:     Jann Horn <jannh@google.com>
Cc:     Kees Cook <keescook@chromium.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Will Drewry <wad@chromium.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] seccomp: Remove bogus __user annotations
Message-ID: <20201120153559.GA4119@sequoia>
References: <20201120015913.1375667-1-jannh@google.com>
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In-Reply-To: <20201120015913.1375667-1-jannh@google.com>
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Hey Jann - Thanks for cleaning this up!

On 2020-11-20 02:59:13, Jann Horn wrote:
> Buffers that are passed to read_actions_logged() and write_actions_logged()
> are in kernel memory; the sysctl core takes care of copying from/to
> userspace.
> 
> Fixes: 0ddec0fc8900 ("seccomp: Sysctl to configure actions that are allowed to be logged")

After tracing back through the code, I was struggling to understand why
I thought the __user annotation was needed back then. It turns out that
__user was correct when I wrote 0ddec0fc8900 and that the Fixes tag
should be changed to this:

 Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")

If you agree, please adjust and resubmit with:

 Reviewed-by: Tyler Hicks <code@tyhicks.com>

Thank you!

Tyler

> Signed-off-by: Jann Horn <jannh@google.com>
> ---
>  kernel/seccomp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index 8ad7a293255a..c2bff3561846 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -1968,7 +1968,7 @@ static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
>  	return true;
>  }
>  
> -static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer,
> +static int read_actions_logged(struct ctl_table *ro_table, void *buffer,
>  			       size_t *lenp, loff_t *ppos)
>  {
>  	char names[sizeof(seccomp_actions_avail)];
> @@ -1986,7 +1986,7 @@ static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer,
>  	return proc_dostring(&table, 0, buffer, lenp, ppos);
>  }
>  
> -static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer,
> +static int write_actions_logged(struct ctl_table *ro_table, void *buffer,
>  				size_t *lenp, loff_t *ppos, u32 *actions_logged)
>  {
>  	char names[sizeof(seccomp_actions_avail)];
> 
> base-commit: 4d02da974ea85a62074efedf354e82778f910d82
> -- 
> 2.29.2.454.gaff20da3a2-goog
>