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

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Date:   Mon, 14 Aug 2023 08:00:22 -0600
From:   Tycho Andersen <tycho@...ho.pizza>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Jürg Billeter <j@...ron.ch>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        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, Aug 14, 2023 at 01:02:35PM +0200, Miklos Szeredi wrote:
> 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.

I agree.

> 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?

It seems like we really do need to wait here. I guess that means we
need some kind of exit-proof wait?

Tycho