From: Theodore Ts'o tytso@mit.edu

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 --- I thought the 4.4.y backport should apply, but I think it doesn't after all. This backport applies to v4.9.y.

fs/ext4/xattr.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index fdcbe0f2814f..c19c96840480 100644 --- 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);