On Tue, Nov 19, 2024 at 05:33:03PM +0300, Vasiliy Kovalev wrote:
> without a lookup operation. Adding the following check in bfs_iget:
>
> struct inode *bfs_iget(struct super_block *sb, unsigned long ino)
> {
>
> ...
> brelse(bh);
>
> + if (S_ISDIR(inode->i_mode) && !inode->i_op->lookup) {
> + printf("Directory inode missing lookup %s:%08lx\n",
> inode->i_sb->s_id, ino);
> + goto error;
> + }
> +
> unlock_new_inode(inode);
> return inode;
>
> error:
> iget_failed(inode);
> return ERR_PTR(-EIO);
> }
>
> prevents the error but exposes an invalid inode:
>
> loop0: detected capacity change from 0 to 64
> BFS-fs: bfs_iget(): Directory inode missing lookup loop0:00000002
> overlayfs: overlapping lowerdir path
>
> Would this be considered a valid workaround, or does BFS require further
> fixes?
Yes, it does. Note that this
inode->i_mode = 0x0000FFFF & le32_to_cpu(di->i_mode);
sets the bits 0..15, which includes not only the permissions
(0..11), but the file type as well. And those |= are not
going to be enough to prevent trouble - what we have there
is
0x1000 => FIFO
0x2000 => CHR
0x4000 => DIR
0x6000 => BLK
0x8000 => REG
0xa000 => LNK
0xe000 => SOCK
So depending upon ->i_vtype you get one of
* ->i_op and ->i_fop set for directory, type bits - 0x4000 | junk
* ->i_op and ->i_fop set for regular file, type bits - 0x8000 | junk
* ->i_op and ->i_fop left empty, type bits - junk.
Frankly, I would rather ignore bits 12..15 (i.e.
inode->i_mode = 0x00000FFF & le32_to_cpu(di->i_mode);
instead of
inode->i_mode = 0x0000FFFF & le32_to_cpu(di->i_mode);
) and complain (and fail) if ->i_vtype value is fucked up.
