Re: [PATCH 1/2] ext4: fail ext4_iget if special inode unallocated
From: Jan Kara
Date: Fri Jan 06 2023 - 09:29:24 EST
On Fri 06-01-23 18:47:05, Baokun Li wrote:
> 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@xxxxxxx>
> Suggested-by: Theodore Ts'o <tytso@xxxxxxx>
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Thanks for the patch! A few comments below.
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 9d9f414f99fe..3f7cfa91ba89 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;
> @@ -4951,10 +4944,13 @@ 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) ||
^ extra parenthesis here ^
> !(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS)) &&
> ino != EXT4_BOOT_LOADER_INO) {
> /* this inode is deleted */
> + if (flags & EXT4_IGET_SPECIAL)
> + ext4_error_inode(inode, function, line, 0,
> + "iget: special inode unallocated");
I think it would be better to return -EFSCORRUPTED and not -ESTALE in this
case.
> ret = -ESTALE;
> goto bad_inode;
> }
Otherwise the patch looks good to me.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR