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Message-ID: <4f66cded234462964899f2a661750d6798a57ec0.camel@bitron.ch>
Subject: [REGRESSION] fuse: execve() fails with ETXTBSY due to async
 fuse_flush
From:   =?ISO-8859-1?Q?J=FCrg?= Billeter <j@bitron.ch>
To:     Miklos Szeredi <miklos@szeredi.hu>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Tycho Andersen <tycho@tycho.pizza>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, regressions@lists.linux.dev
Date:   Mon, 14 Aug 2023 08:03:29 +0200
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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.

I've confirmed that this issue is absent in v6.2 and reverting
5a8bee63b1 on top of v6.4.10 fixes the regression.

#regzbot introduced: 5a8bee63b1

J=C3=BCrg