ext4: fail ext4_iget if special inode unallocated

[ Upstream commit 5cd740287ae5e3f9d1c46f5bfe8778972fd6d3fe ]

In ext4_fill_super(), EXT4_ORPHAN_FS flag is cleared after
ext4_orphan_cleanup() is executed. Therefore, when __ext4_iget() is
called to get an inode whose i_nlink is 0 when the flag exists, no error
is returned. If the inode is a special inode, a null pointer dereference
may occur. If the value of i_nlink is 0 for any inodes (except boot loader
inodes) got by using the EXT4_IGET_SPECIAL flag, the current file system
is corrupted. Therefore, make the ext4_iget() function return an error if
it gets such an abnormal special inode.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=199179
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216541
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216539
Reported-by: Luís Henriques <lhenriques@suse.de>
Suggested-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230107032126.4165860-2-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 34c87fc..eea11ad 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4807,13 +4807,6 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
                goto bad_inode;
        raw_inode = ext4_raw_inode(&iloc);
 
-       if ((ino == EXT4_ROOT_INO) && (raw_inode->i_links_count == 0)) {
-               ext4_error_inode(inode, function, line, 0,
-                                "iget: root inode unallocated");
-               ret = -EFSCORRUPTED;
-               goto bad_inode;
-       }
-
        if ((flags & EXT4_IGET_HANDLE) &&
            (raw_inode->i_links_count == 0) && (raw_inode->i_mode == 0)) {
                ret = -ESTALE;
@@ -4886,11 +4879,16 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
         * NeilBrown 1999oct15
         */
        if (inode->i_nlink == 0) {
-               if ((inode->i_mode == 0 ||
+               if ((inode->i_mode == 0 || flags & EXT4_IGET_SPECIAL ||
                     !(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS)) &&
                    ino != EXT4_BOOT_LOADER_INO) {
-                       /* this inode is deleted */
-                       ret = -ESTALE;
+                       /* this inode is deleted or unallocated */
+                       if (flags & EXT4_IGET_SPECIAL) {
+                               ext4_error_inode(inode, function, line, 0,
+                                                "iget: special inode unallocated");
+                               ret = -EFSCORRUPTED;
+                       } else
+                               ret = -ESTALE;
                        goto bad_inode;
                }
                /* The only unlinked inodes we let through here have