[PATCH AUTOSEL 6.2 05/13] ext4: fail ext4_iget if special inode unallocated

Sasha Levin
2023-03-14T12:56:35Z

From: Baokun Li <libaokun1@huawei.com>

[ 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>
---
fs/ext4/inode.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9d9f414f99fec..ed7598127e7c5 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4872,13 +4872,6 @@ 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;
@@ -4951,11 +4944,16 @@ 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
--
2.39.2