[PATCH 3.16 35/63] ext4: add more inode number paranoia checks

[Ben Hutchings]

3.16.58-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Theodore Ts'o <tytso@xxxxxxx>

commit c37e9e013469521d9adb932d17a1795c139b36db upstream.

If there is a directory entry pointing to a system inode (such as a
journal inode), complain and declare the file system to be corrupted.

Also, if the superblock's first inode number field is too small,
refuse to mount the file system.

This addresses CVE-2018-10882.

https://bugzilla.kernel.org/show_bug.cgi?id=200069

Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/ext4/ext4.h  | 5 -----
 fs/ext4/inode.c | 3 ++-
 fs/ext4/super.c | 5 +++++
 3 files changed, 7 insertions(+), 6 deletions(-)

--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1422,11 +1422,6 @@ static inline struct timespec ext4_curre
 static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
 {
 	return ino == EXT4_ROOT_INO ||
-		ino == EXT4_USR_QUOTA_INO ||
-		ino == EXT4_GRP_QUOTA_INO ||
-		ino == EXT4_BOOT_LOADER_INO ||
-		ino == EXT4_JOURNAL_INO ||
-		ino == EXT4_RESIZE_INO ||
 		(ino >= EXT4_FIRST_INO(sb) &&
 		 ino <= le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count));
 }
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3957,7 +3957,8 @@ static int __ext4_get_inode_loc(struct i
 	int			inodes_per_block, inode_offset;
 
 	iloc->bh = NULL;
-	if (!ext4_valid_inum(sb, inode->i_ino))
+	if (inode->i_ino < EXT4_ROOT_INO ||
+	    inode->i_ino > le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count))
 		return -EIO;
 
 	iloc->block_group = (inode->i_ino - 1) / EXT4_INODES_PER_GROUP(sb);
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3771,6 +3771,11 @@ static int ext4_fill_super(struct super_
 	} else {
 		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
 		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
+		if (sbi->s_first_ino < EXT4_GOOD_OLD_FIRST_INO) {
+			ext4_msg(sb, KERN_ERR, "invalid first ino: %u",
+				 sbi->s_first_ino);
+			goto failed_mount;
+		}
 		if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
 		    (!is_power_of_2(sbi->s_inode_size)) ||
 		    (sbi->s_inode_size > blocksize)) {