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	Tue, 29 Sep 2026 13:51:54 +0000
Date: Tue, 29 Sep 2026 14:51:54 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: Gary Guo <gary@garyguo.net>
Cc: Christian Brauner <brauner@kernel.org>,
	Alice Ryhl <aliceryhl@google.com>,
	Georgios Androutsopoulos <georgeandrout13@gmail.com>,
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	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <lossin@kernel.org>,
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	Trevor Gross <tmgross@umich.edu>,
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	Alexandre Courbot <acourbot@nvidia.com>,
	Onur =?iso-8859-1?Q?=D6zkan?= <work@onurozkan.dev>,
	linux-fsdevel@vger.kernel.org, rust-for-linux@vger.kernel.org,
	linux-kernel@vger.kernel.org, Al Viro <viro@ftp.linux.org.uk>
Subject: Re: [PATCH v2] rust: file: handle fd table teardown in file
 descriptor APIs
Message-ID: <20260929135154.GB989762@ZenIV>
References: <20260923022339.3340694-1-georgeandrout13@gmail.com>
 <arThye_219ruNbM2@google.com>
 <20260925-stellen-brummen-festrede-266af0305ac7@brauner>
 <20260929044843.GA3909609@ZenIV>
 <DLRSQRUVOGT2.10ZY01VEJVHCE@garyguo.net>
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Tue, Sep 29, 2026 at 01:24:45PM +0100, Gary Guo wrote:

> > 	In particular, ->release() mentioned upthread should not be allowed
> > to access _anything_ hanging off current, not just descriptor table.  Note
> > that the last reference to an opened file might be sitting in an SCM_RIGHTS
> > datagram pruned by AF_UNIX garbage collector; as far as the method is concerned,
> > it might be called from random thread.
> 
> This part is protected -- we mark FileDescriptionReservation as `!Send` which
> prevents it being moved to another task. We also take care to make sure that
> the task returned `current!()` is not allowed to be used outside the current
> task.

Not the point - ->release() can't make any assumptions regarding which thread
it will be run in.  current won't change under it, but there's nothing
useful you could want with it.  If it has non-NULL ->files (or ->mm, or...),
that reference will also remain stable, but any attempt to do anything with
it would be a bug.