linux-kernel - Re: [PATCH v3 2/2] sysctl: Fix underflow value setting risk in vm

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Message-ID: <20241218124138.lxelrc6z6lc6cin5@quack3>
Date: Wed, 18 Dec 2024 13:41:38 +0100
From: Jan Kara <jack@...e.cz>
To: nicolas.bouchinet@...p-os.org
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Luis Chamberlain <mcgrof@...nel.org>, Kees Cook <kees@...nel.org>,
	Joel Granados <j.granados@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Neil Horman <nhorman@...driver.com>, Lin Feng <linf@...gsu.com>,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v3 2/2] sysctl: Fix underflow value setting risk in
 vm_table

On Tue 17-12-24 14:29:07, nicolas.bouchinet@...p-os.org wrote:
> From: Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>
> 
> Commit 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in vm_table")
> fixes underflow value setting risk in vm_table but misses vdso_enabled
> sysctl.
> 
> vdso_enabled sysctl is initialized with .extra1 value as SYSCTL_ZERO to
> avoid negative value writes but the proc_handler is proc_dointvec and
> not proc_dointvec_minmax and thus do not uses .extra1 and .extra2.
> 
> The following command thus works :
> 
> `# echo -1 > /proc/sys/vm/vdso_enabled`
> 
> This patch properly sets the proc_handler to proc_dointvec_minmax.
> 
> Fixes: 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in vm_table")
> Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  kernel/sysctl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 79e6cb1d5c48f..6d8a4fceb79aa 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2194,8 +2194,9 @@ static struct ctl_table vm_table[] = {
>  		.maxlen		= sizeof(vdso_enabled),
>  #endif
>  		.mode		= 0644,
> -		.proc_handler	= proc_dointvec,
> +		.proc_handler	= proc_dointvec_minmax,
>  		.extra1		= SYSCTL_ZERO,
> +		.extra1		= SYSCTL_ONE,
>  	},
>  #endif
>  	{
> -- 
> 2.47.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR