Re: [PATCH][RFC] race in exportfs_decode_fh()

[Linus Torvalds]

On Fri, Nov 8, 2019 at 7:13 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> We have derived the parent from fhandle, we have a disconnected dentry for child,
> we go look for the name.  We even find it.  Now, we want to look it up.  And
> some bastard goes and unlinks it, just as we are trying to lock the parent.
> We do a lookup, and get a negative dentry.  Then we unlock the parent... and
> some other bastard does e.g. mkdir with the same name.  OK, nresult->d_inode
> is not NULL (anymore).  It has fuck-all to do with the original fhandle
> (different inumber, etc.) but we happily accept it.

No arguments with your patch, although I doubt that this case has
actually ever happened in practice ;)

              Linus