ext4: never move the system.data xattr out of the inode body

commit 8cdb5240ec5928b20490a2bb34cb87e9a5f40226 upstream.

When expanding the extra isize space, we must never move the
system.data xattr out of the inode body.  For performance reasons, it
doesn't make any sense, and the inline data implementation assumes
that system.data xattr is never in the external xattr block.

This addresses CVE-2018-10880

https://bugzilla.kernel.org/show_bug.cgi?id=200005

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
[groeck: Context changes]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index fdcbe0f2814f8875ee6d9f3be801021817f20629..c19c96840480a66acfce9a830fe3c4cd02a488dc 100644 (file)
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1426,6 +1426,11 @@ static int ext4_xattr_make_inode_space(handle_t *handle, struct inode *inode,
                last = IFIRST(header);
                /* Find the entry best suited to be pushed into EA block */
                for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
+                       /* never move system.data out of the inode */
+                       if ((last->e_name_len == 4) &&
+                           (last->e_name_index == EXT4_XATTR_INDEX_SYSTEM) &&
+                           !memcmp(last->e_name, "data", 4))
+                               continue;
                        total_size =
                        EXT4_XATTR_SIZE(le32_to_cpu(last->e_value_size)) +
                                        EXT4_XATTR_LEN(last->e_name_len);