linux-kernel - Re: [REGRESSION] fuse: execve() fails with ETXTBSY due to async fuse

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Message-ID: <CAJfpeguG4f4S-pq+_EXHxfB63mbof-VnaOy-7a-7seWLMj_xyQ@mail.gmail.com>
Date:   Mon, 14 Aug 2023 13:02:35 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Jürg Billeter <j@...ron.ch>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Tycho Andersen <tycho@...ho.pizza>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        regressions@...ts.linux.dev
Subject: Re: [REGRESSION] fuse: execve() fails with ETXTBSY due to async fuse_flush

On Mon, 14 Aug 2023 at 08:03, Jürg Billeter <j@...ron.ch> wrote:
>
> Since v6.3-rc1 commit 5a8bee63b1 ("fuse: in fuse_flush only wait if
> someone wants the return code") `fput()` is called asynchronously if a
> file is closed as part of a process exiting, i.e., if there was no
> explicit `close()` before exit.
>
> If the file was open for writing, also `put_write_access()` is called
> asynchronously as part of the async `fput()`.
>
> If that newly written file is an executable, attempting to `execve()`
> the new file can fail with `ETXTBSY` if it's called after the writer
> process exited but before the async `fput()` has run.

Thanks for the report.

At this point, I think it would be best to revert the original patch,
since only v6.4 has it.

The original fix was already a workaround, and I don't see a clear
path forward in this direction.  We need to see if there's better
direction.

Ideas?

Thanks,
Miklos