linux-kernel - Re: [PATCH] fuse: Send FUSE_WRITE_KILL

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Message-ID: <CAJfpegsXXGcZDbbtDoXG8sQqHrAS1fs-TsRz5ndQ62sse1Av_w@mail.gmail.com>
Date:   Mon, 21 Jun 2021 10:26:52 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Connor Kuehl <ckuehl@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fuse: Send FUSE_WRITE_KILL_SUIDGID for killpriv v1

On Fri, 23 Apr 2021 at 17:19, Connor Kuehl <ckuehl@...hat.com> wrote:
>
> FUSE doesn't seem to be adding the FUSE_WRITE_KILL_SUIDGID flag on write
> requests for FUSE connections that support FUSE_HANDLE_KILLPRIV but not
> FUSE_HANDLE_KILLPRIV_V2.
>
> However, the FUSE userspace header states:
>
>         FUSE_HANDLE_KILLPRIV: fs handles killing suid/sgid/cap on
>         write/chown/trunc
>         ^^^^^
>
> To improve backwards compatibility with file servers that don't support
> FUSE_HANDLE_KILLPRIV_V2, add the FUSE_WRITE_KILL_SUIDGID flag to write
> requests if FUSE_HANDLE_KILLPRIV has been negotiated -OR- if the
> conditions for FUSE_HANDLE_KILLPRIV_V2 support are met.


If server does not support FUSE_HANDLE_KILLPRIV_V2, then it does not
support FUSE_WRITE_KILL_SUIDGID either.  The two were introduced
together and the latter is only meaningful if the
FUSE_HANDLE_KILLPRIV_V2 feature was negotiated.

What am I missing?

Thanks,
Miklos