From: Al Viro <viro@zeniv.linux.org.uk>
To: Jann Horn <jannh@google.com>
Cc: Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Chuck Lever <chuck.lever@oracle.com>,
Jeff Layton <jlayton@kernel.org>,
Amir Goldstein <amir73il@gmail.com>,
linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh()
Date: Wed, 3 Jun 2026 19:15:23 +0100 [thread overview]
Message-ID: <20260603181523.GW2636677@ZenIV> (raw)
In-Reply-To: <20260603-vfs-fhandle-uaf-fix-v1-1-ff64ee367e4d@google.com>
On Wed, Jun 03, 2026 at 07:38:06PM +0200, Jann Horn wrote:
> Fix it by taking rcu_read_lock() around the mount::mnt_ns access, like
> in __prepend_path().
> + /*
> + * Containing namespace.
> + * Normally protected by namespace_sem, but there are also lockless
> + * readers (which must use RCU to guard against the namespace being
> + * freed).
> + */
> + struct mnt_namespace *mnt_ns;
Umm... It's somewhat subtle - at the very least you need to explain why
there will be an RCU delay between umount_tree() clearing that and
having the sucker freed.
next prev parent reply other threads:[~2026-06-03 18:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-03 17:38 [PATCH] fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh() Jann Horn
2026-06-03 18:15 ` Al Viro [this message]
2026-06-03 18:23 ` Jann Horn
2026-06-03 18:41 ` Al Viro
2026-06-03 18:50 ` Al Viro
2026-06-03 18:24 ` Al Viro
2026-06-03 18:46 ` Jann Horn
2026-06-03 18:53 ` Al Viro
2026-06-03 19:02 ` Al Viro
2026-06-03 19:08 ` Jann Horn
2026-06-03 19:14 ` Jann Horn
2026-06-04 7:56 ` Christian Brauner
2026-06-03 19:25 ` Al Viro
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