linux-ext4 - Re: [PATCH 08/13] nfs: fix UAF on pathwalk running into umount

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Date: Mon, 5 Feb 2024 13:29:49 +0100
From: Christian Brauner <brauner@...nel.org>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: linux-fsdevel@...r.kernel.org, 
	Linus Torvalds <torvalds@...ux-foundation.org>, linux-ext4@...r.kernel.org, linux-nfs@...r.kernel.org, 
	Miklos Szeredi <miklos@...redi.hu>, linux-cifs@...r.kernel.org
Subject: Re: [PATCH 08/13] nfs: fix UAF on pathwalk running into umount

On Sun, Feb 04, 2024 at 02:17:34AM +0000, Al Viro wrote:
> NFS ->d_revalidate(), ->permission() and ->get_link() need to access
> some parts of nfs_server when called in RCU mode:
> 	server->flags
> 	server->caps
> 	*(server->io_stats)
> and, worst of all, call
> 	server->nfs_client->rpc_ops->have_delegation
> (the last one - as NFS_PROTO(inode)->have_delegation()).  We really
> don't want to RCU-delay the entire nfs_free_server() (it would have
> to be done with schedule_work() from RCU callback, since it can't
> be made to run from interrupt context), but actual freeing of
> nfs_server and ->io_stats can be done via call_rcu() just fine.
> nfs_client part is handled simply by making nfs_free_client() use
> kfree_rcu().
> 
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
> ---

Acked-by: Christian Brauner <brauner@...nel.org>