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Re: [Patch] quota: do not leak info to user-space

To: Cong Wang <amwang@xxxxxxxxxx>
Subject: Re: [Patch] quota: do not leak info to user-space
From: Jan Kara <jack@xxxxxxx>
Date: Mon, 13 May 2013 12:04:23 +0200
Cc: linux-kernel@xxxxxxxxxxxxxxx, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Jan Kara <jack@xxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1368177873-4819-1-git-send-email-amwang@xxxxxxxxxx>
References: <1368177873-4819-1-git-send-email-amwang@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Fri 10-05-13 17:24:33, Cong Wang wrote:
> From: Cong Wang <amwang@xxxxxxxxxx>
> 
> There is a hole in struct fs_quota_stat, so we have to
> zero the struct on stack before copying it to user-space.
> 
> Cc: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Cong Wang <amwang@xxxxxxxxxx>
  Good point. I've merged the patch.

BTW for XFS folks: The structure definition looks somewhat odd (unaligned
definition of qs_flags, qs_uquota starts only at 32-bit boundary although
it has 64-bit fields in it) and I wouldn't be surprised if it needed compat
wrapper for 32-bit apps on some architectures...

                                                                Honza
> 
> ---
> diff --git a/fs/quota/quota.c b/fs/quota/quota.c
> index c7314f1..2b0c182 100644
> --- a/fs/quota/quota.c
> +++ b/fs/quota/quota.c
> @@ -211,6 +211,7 @@ static int quota_getxstate(struct super_block *sb, void 
> __user *addr)
>  
>       if (!sb->s_qcop->get_xstate)
>               return -ENOSYS;
> +     memset(&fqs, 0, sizeof(fqs));
>       ret = sb->s_qcop->get_xstate(sb, &fqs);
>       if (!ret && copy_to_user(addr, &fqs, sizeof(fqs)))
>               return -EFAULT;
-- 
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR

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