linux-kernel - Re: [PATCH 2/3] sysctl: Fix underflow value setting risk in vm

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Message-ID: <97eed46f-0088-4183-aef4-d6b5c942f074@wangsu.com>
Date: Wed, 13 Nov 2024 10:37:32 +0800
From: Lin Feng <linf@...gsu.com>
To: nicolas.bouchinet@...p-os.org, linux-kernel@...r.kernel.org,
 linux-serial@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc: 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>, Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 2/3] sysctl: Fix underflow value setting risk in vm_table

Thanks!

Reviewed-by: Lin Feng <linf@...gsu.com>

On 11/12/24 21:13, 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>
> ---
>  kernel/sysctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 79e6cb1d5c48f..37b1c1a760985 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2194,7 +2194,7 @@ 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,
>  	},
>  #endif