From: Miklos Szeredi <mszeredi@redhat.com>
To: David Howells <dhowells@redhat.com>
Cc: viro <viro@zeniv.linux.org.uk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-nfs@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/9] VFS: Introduce a mount context
Date: Tue, 9 May 2017 14:02:57 +0200 [thread overview]
Message-ID: <CAOssrKeR4bNwYyuwyr2d5fG8RcxeyWKREFTdnGqovus9t_2n4A@mail.gmail.com> (raw)
In-Reply-To: <15762.1494322915@warthog.procyon.org.uk>
On Tue, May 9, 2017 at 11:41 AM, David Howells <dhowells@redhat.com> wrote:
> Miklos Szeredi <mszeredi@redhat.com> wrote:
>
>> I think that's crazy. We don't return detailed errors for any other
>> syscall for path lookup, so why would path lookup for mount be
>> special.
>
> Firstly, we don't return detailed errors for mount() at the moment either.
>
> Secondly, path lookup might entail automounts, so perhaps we should do it for
> path lookup too. Particularly in light of the fact that NFS4 mount uses
> pathwalk to get from server:/ to server:/the/dir/I/actually/wanted/ so I'm
> currently losing that error:-/
>
> Thirdly, the security operation I'm talking about is separate to path lookup -
> though perhaps we should pass LOOKUP_MOUNT as an intent flag into pathwalk so
> that the security check can be done there; perhaps combined with another one.
>
> Fourthly, why shouldn't we consider extending the facility to other system
> calls in future? It would involve copying the string to task_struct and
> providing a way to retrieve it, but that's not that hard to achieve.
Maybe we should. In fact that sounds like a splendid idea. IMO even
better, than having errors go via the fsfd descriptor. Pretty cheap
on the kernel side, and completely optional on the userspace side.
>
>> And why would
>>
>> fd = open("/foo/bar", O_PATH);
>> fsmount(fsfd, fd, NULL);
>>
>> behave differently from
>>
>> fsmount(fsfd, -1, "/foo/bar");
>>
>> ?
>
> There's argument that the former should return EFAULT. And that you should
> set the path to "" and pass AT_EMPTY_PATH. I should probably make sure it
> does that - and add a flags field. statx() was fixed to work this way.
>
> Question for you: Should the MNT_* flags be passed to fsmount(), perhaps in
> MS_* form?
MS_* flags are a mess. I don't think they should be used for any new
functionality. MNT_* flags are much better, but there are some
internal flags there as well.
I think the struct file model is better, where we have the external
O_* flags and the internal FMODE_* flags.
Thanks,
Miklos
next prev parent reply other threads:[~2017-05-09 12:03 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-03 16:04 [RFC][PATCH 0/9] VFS: Introduce mount context David Howells
2017-05-03 16:04 ` [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data David Howells
2017-05-03 16:55 ` Jeff Layton
2017-05-03 19:26 ` Rasmus Villemoes
2017-05-03 20:13 ` David Howells
2017-05-03 16:04 ` [PATCH 2/9] Clean up whitespace in fs/namespace.c David Howells
2017-05-03 16:04 ` [PATCH 3/9] VFS: Introduce a mount context David Howells
2017-05-03 18:13 ` Jeff Layton
2017-05-03 18:26 ` Joe Perches
2017-05-03 20:38 ` Matthew Wilcox
2017-05-03 21:36 ` Joe Perches
2017-05-04 6:28 ` Julia Lawall
2017-05-03 21:17 ` David Howells
2017-05-03 18:37 ` David Howells
2017-05-03 18:43 ` Joe Perches
2017-05-03 20:11 ` David Howells
2017-05-04 9:27 ` David Howells
2017-05-04 14:34 ` Joe Perches
2017-05-03 21:43 ` Rasmus Villemoes
2017-05-04 10:22 ` David Howells
2017-05-08 15:05 ` Miklos Szeredi
2017-05-08 22:57 ` David Howells
2017-05-09 8:03 ` Miklos Szeredi
2017-05-10 12:41 ` Karel Zak
2017-05-09 9:32 ` David Howells
2017-05-09 11:04 ` Miklos Szeredi
2017-05-09 9:41 ` David Howells
2017-05-09 12:02 ` Miklos Szeredi [this message]
2017-05-09 18:51 ` Jeff Layton
2017-05-10 7:24 ` Miklos Szeredi
2017-05-10 8:05 ` David Howells
2017-05-10 13:20 ` Jeff Layton
2017-05-10 13:30 ` Miklos Szeredi
2017-05-10 13:33 ` Miklos Szeredi
2017-05-10 13:48 ` Jeff Layton
2017-05-12 8:15 ` Miklos Szeredi
2017-05-10 13:31 ` David Howells
2017-05-10 13:37 ` Jeff Layton
2017-05-09 9:56 ` David Howells
2017-05-09 12:38 ` Miklos Szeredi
2017-05-03 16:05 ` [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells
2017-05-03 18:37 ` Jeff Layton
2017-05-03 18:41 ` David Howells
2017-05-03 20:44 ` Rasmus Villemoes
2017-05-04 10:40 ` Karel Zak
2017-05-04 12:55 ` David Howells
2017-05-04 12:58 ` David Howells
2017-05-04 13:06 ` David Howells
2017-05-04 13:34 ` Karel Zak
2017-05-09 18:40 ` Jeff Layton
2017-05-08 15:10 ` Miklos Szeredi
2017-05-08 23:09 ` David Howells
2017-05-03 16:05 ` [PATCH 5/9] Implement fsmount() to effect a pre-configured mount David Howells
2017-05-03 16:05 ` [PATCH 6/9] Sample program for driving fsopen/fsmount David Howells
2017-05-03 16:05 ` [PATCH 7/9] procfs: Move proc_fill_super() to fs/proc/root.c David Howells
2017-05-03 16:05 ` [PATCH 8/9] proc: Support the mount context in procfs David Howells
2017-05-03 16:05 ` [PATCH 9/9] NFS: Support the mount context and fsopen() David Howells
2017-05-03 16:44 ` [RFC][PATCH 0/9] VFS: Introduce mount context Jeff Layton
2017-05-03 16:50 ` David Howells
2017-05-03 17:27 ` Jeff Layton
2017-05-05 14:35 ` Miklos Szeredi
2017-05-05 15:47 ` David Howells
2017-05-08 8:25 ` Miklos Szeredi
2017-05-08 8:35 ` David Howells
2017-05-08 8:43 ` Miklos Szeredi
2017-05-08 17:03 ` Djalal Harouni
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