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
Signed-off-by: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 9fb2a75..b51bb73 100644 (file)
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1386,6 +1386,11 @@ retry:
                /* Find the entry best suited to be pushed into EA block */
                entry = NULL;
                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);