Re: [PATCH v2] fuse: fix illegal access to inode with reused nodeid

[Miklos Szeredi <miklos@szeredi.hu>]

On Mon, 21 Jun 2021 at 13:03, Amir Goldstein <amir73il@gmail.com> wrote:
>
> Server responds to LOOKUP and other ops (READDIRPLUS/CREATE/MKNOD/...)
> with ourarg containing nodeid and generation.
>
> If a fuse inode is found in inode cache with the same nodeid but
> different generation, the existing fuse inode should be unhashed and
> marked "bad" and a new inode with the new generation should be hashed
> instead.
>
> This can happen, for example, with passhrough fuse filesystem that
> returns the real filesystem ino/generation on lookup and where real inode
> numbers can get recycled due to real files being unlinked not via the fuse
> passthrough filesystem.
>
> With current code, this situation will not be detected and an old fuse
> dentry that used to point to an older generation real inode, can be used
> to access a completely new inode, which should be accessed only via the
> new dentry.
>
> Note that because the FORGET message carries the nodeid w/o generation,
> the server should wait to get FORGET counts for the nlookup counts of
> the old and reused inodes combined, before it can free the resources
> associated to that nodeid.
>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Applied and pushed.

Thanks,
Miklos