On Mon, 18 Nov 2024 at 19:54, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> Can you analyse what went wrong with the reproducer?
> How did we get to a state where lowerstack of parent
> has a dentry which is !d_can_lookup?
Theoretically we could still get a an S_ISDIR inode, because
ovl_get_inode() doesn't look at the is_dir value that lookup found.
I.e. lookup thinks it found a non-dir, but iget will create a dir
because of the backing inode's type.
AFAICS this can only happen if i_op->lookup is not set on S_ISDIR for
the backing inode, which shouldn't happen on normal filesystems.
Reproducer seems to use bfs, which *should* be normal, and bfs_iget
certainly doesn't do anything weird in that case, so I still don't
understand what is happening.
In any case something like the following should filter out such weirdness:
bool ovl_dentry_weird(struct dentry *dentry)
{
+ if (!d_can_lookup(dentry) && !d_is_file(dentry) &&
!d_is_symlink(dentry))
+ return true;
+
return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
Thanks,
Miklos
