[PATCH 4.17 18/70] ext4: do not allow external inodes for inline data

[Greg Kroah-Hartman]

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso@xxxxxxx>

commit 117166efb1ee8f13c38f9e96b258f16d4923f888 upstream.

The inline data feature was implemented before we added support for
external inodes for xattrs.  It makes no sense to support that
combination, but the problem is that there are a number of extended
attribute checks that are skipped if e_value_inum is non-zero.

Unfortunately, the inline data code is completely e_value_inum
unaware, and attempts to interpret the xattr fields as if it were an
inline xattr --- at which point, Hilarty Ensues.

This addresses CVE-2018-11412.

https://bugzilla.kernel.org/show_bug.cgi?id=199803

Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
Cc: stable@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/ext4/inline.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -144,6 +144,12 @@ int ext4_find_inline_data_nolock(struct
 		goto out;
 
 	if (!is.s.not_found) {
+		if (is.s.here->e_value_inum) {
+			EXT4_ERROR_INODE(inode, "inline data xattr refers "
+					 "to an external xattr inode");
+			error = -EFSCORRUPTED;
+			goto out;
+		}
 		EXT4_I(inode)->i_inline_off = (u16)((void *)is.s.here -
 					(void *)ext4_raw_inode(&is.iloc));
 		EXT4_I(inode)->i_inline_size = EXT4_MIN_INLINE_DATA_SIZE +