linux-ext4 - [PATCH] ext4: disallow files with EXT4_JOURNAL_DATA_FL from EXT4_IOC_SWAP

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Date:   Mon, 11 Feb 2019 01:15:37 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
CC:     <yangerkun@...wei.com>, <jack@...e.com>, <miaoxie@...wei.com>,
        <yi.zhang@...wei.com>, <houtao1@...wei.com>,
        Theodore Ts'o <tytso@....edu>
Subject: [PATCH] ext4: disallow files with EXT4_JOURNAL_DATA_FL from EXT4_IOC_SWAP_BOOT

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@....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;
-- 
2.19.1