From: Al Viro <viro@zeniv.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Amir Goldstein <amir73il@gmail.com>,
Christian Brauner <brauner@kernel.org>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
"Serge E . Hallyn" <serge@hallyn.com>,
Mimi Zohar <zohar@linux.ibm.com>,
linux-security-module@vger.kernel.org,
linux-integrity@vger.kernel.org, linux-unionfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v3 3/3] fs: store real path instead of fake path in backing file f_path
Date: Tue, 10 Oct 2023 18:41:46 +0100 [thread overview]
Message-ID: <20231010174146.GQ800259@ZenIV> (raw)
In-Reply-To: <20231010165504.GP800259@ZenIV>
On Tue, Oct 10, 2023 at 05:55:04PM +0100, Al Viro wrote:
> On Tue, Oct 10, 2023 at 03:34:45PM +0200, Miklos Szeredi wrote:
> > On Tue, 10 Oct 2023 at 15:17, Amir Goldstein <amir73il@gmail.com> wrote:
> >
> > > Sorry, you asked about ovl mount.
> > > To me it makes sense that if users observe ovl paths in writable mapped
> > > memory, that ovl should not be remounted RO.
> > > Anyway, I don't see a good reason to allow remount RO for ovl in that case.
> > > Is there?
> >
> > Agreed.
> >
> > But is preventing remount RO important enough to warrant special
> > casing of backing file in generic code? I'm not convinced either
> > way...
>
> You definitely want to guarantee that remounting filesystem r/o
> prevents the changes of visible contents; it's not just POSIX,
> it's a fairly basic common assumption about any local filesystems.
Incidentally, could we simply keep a reference to original struct file
instead of messing with path?
The only caller of backing_file_open() gets &file->f_path as user_path; how
about passing file instead, and having backing_file_open() do get_file()
on it and stash the sucker into your object?
And have put_file_access() do
if (unlikely(file->f_mode & FMODE_BACKING))
fput(backing_file(file)->file);
in the end.
No need to mess with write access in any special way and it's closer
to the semantics we have for normal mmap(), after all - it keeps the
file we'd passed to it open as long as mapping is there.
Comments?
next prev parent reply other threads:[~2023-10-10 17:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-09 15:37 [PATCH v3 0/3] Reduce impact of overlayfs backing files fake path Amir Goldstein
2023-10-09 15:37 ` [PATCH v3 1/3] fs: get mnt_writers count for an open backing file's real path Amir Goldstein
2023-10-09 15:37 ` [PATCH v3 2/3] fs: create helper file_user_path() for user displayed mapped file path Amir Goldstein
2023-10-09 15:37 ` [PATCH v3 3/3] fs: store real path instead of fake path in backing file f_path Amir Goldstein
2023-10-10 11:59 ` Miklos Szeredi
2023-10-10 13:10 ` Amir Goldstein
2023-10-10 13:17 ` Amir Goldstein
2023-10-10 13:34 ` Miklos Szeredi
2023-10-10 15:22 ` Amir Goldstein
2023-10-10 16:55 ` Al Viro
2023-10-10 17:41 ` Al Viro [this message]
2023-10-10 17:57 ` Amir Goldstein
2023-10-10 18:21 ` Al Viro
2023-10-10 18:28 ` Amir Goldstein
2023-10-11 1:26 ` Al Viro
2023-10-10 18:14 ` Miklos Szeredi
2023-10-11 1:37 ` Al Viro
2023-10-10 11:52 ` [PATCH v3 0/3] Reduce impact of overlayfs backing files fake path Christian Brauner
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