Subject: Re: [PATCH] ext4: disallow files with EXT4_JOURNAL_DATA_FL from
 EXT4_IOC_SWAP_BOOT
To:     Theodore Ts'o <tytso@mit.edu>,
        Ext4 Developers List <linux-ext4@vger.kernel.org>
CC:     <jack@suse.com>, <miaoxie@huawei.com>, <yi.zhang@huawei.com>,
        <houtao1@huawei.com>
References: <20190211061537.32386-1-tytso@mit.edu>
From:   yangerkun <yangerkun@huawei.com>
Message-ID: <bc382233-35ff-943e-d9f7-b17f9dce193d@huawei.com>
Date:   Tue, 12 Feb 2019 20:41:23 +0800
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Reviewed-by: yangerkun <yangerkun@huawei.com>

Theodore Ts'o wrote on 2019/2/11 14:15:
> A malicious/clueless root user can use EXT4_IOC_SWAP_BOOT to force a
> corner casew which can lead to the file system getting corrupted.
> There's no usefulness to allowing this, so just prohibit this case.
> 
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> ---
>   fs/ext4/ioctl.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index 2e76fb55d94a..eb8ca8d80885 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -132,6 +132,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
>   
>   	if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode) ||
>   	    IS_SWAPFILE(inode) || IS_ENCRYPTED(inode) ||
> +	    (EXT4_I(inode)->i_flags & EXT4_JOURNAL_DATA_FL) ||
>   	    ext4_has_inline_data(inode)) {
>   		err = -EINVAL;
>   		goto journal_err_out;
>