Commit 20ba6f8a authored Jan 07, 2023 by Baokun Li Committed by Greg Kroah-Hartman Mar 22, 2023

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>

parent ab519e29

fs/ext4/inode.c

+8 −10

Original line number	Diff line number	Diff line
		@@ -4944,13 +4944,6 @@ 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;
		@@ -5021,10 +5014,15 @@ 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 */
		/* 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;
		}