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From 1f5a81e41f8b1a782c68d3843e9ec1bfaadf7d72 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Wed, 2 Jun 2010 22:04:39 -0400
Subject: ext4: Make sure the MOVE_EXT ioctl can't overwrite append-only files

From: Theodore Ts'o <tytso@mit.edu>

commit 1f5a81e41f8b1a782c68d3843e9ec1bfaadf7d72 upstream.

Dan Roseberg has reported a problem with the MOVE_EXT ioctl.  If the
donor file is an append-only file, we should not allow the operation
to proceed, lest we end up overwriting the contents of an append-only
file.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 fs/ext4/move_extent.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -959,6 +959,9 @@ mext_check_arguments(struct inode *orig_
 		return -EINVAL;
 	}
 
+	if (IS_IMMUTABLE(donor_inode) || IS_APPEND(donor_inode))
+		return -EPERM;
+
 	/* Ext4 move extent does not support swapfile */
 	if (IS_SWAPFILE(orig_inode) || IS_SWAPFILE(donor_inode)) {
 		ext4_debug("ext4 move extent: The argument files should "