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From: Ian Kent <raven@themaw.net>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Aleksa Sarai <cyphar@cyphar.com>,
	David Howells <dhowells@redhat.com>,
	Eric Biederman <ebiederm@xmission.com>,
	stable <stable@vger.kernel.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Serge Hallyn <serge@hallyn.com>,
	dev@opencontainers.org,
	Linux Containers <containers@lists.linux-foundation.org>,
	Linux API <linux-api@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC 0/1] mount: universally disallow mounting over symlinks
Date: Tue, 14 Jan 2020 08:25:19 +0800	[thread overview]
Message-ID: <19fa114ef619057c0d14dc1a587d0ae9ad67dc6d.camel@themaw.net> (raw)
In-Reply-To: <800d36a0dccd43f1b61cab6332a6252ab9aab73c.camel@themaw.net>

On Mon, 2020-01-13 at 10:59 +0800, Ian Kent wrote:
> 
> > 3) is _anything_ besides root directory ever created in direct
> > autofs
> > superblocks by anyone?  If not, why does autofs_lookup() even
> > bother
> > to
> > do anything there?  IOW, why not have it return ERR_PTR(-ENOENT)
> > immediately
> > for direct ones?  Or am I missing something and it is, in fact,
> > possible
> > to have the daemon create something in those?
> 
> Short answer is no, longer answer is directories "shouldn't" ever
> be created inside direct mount points.
> 
> The thing is that the multi-mount map construct can be used with
> direct mounts too, but they must always have a real mount at the
> base because they are direct mounts. So processes should not be
> able to walk into them while they are being mounted (constructed).
> 
> But I'm pretty sure it's rare (maybe not done at all) that this
> map construct is used with direct mounts.

This isn't right.

There's actually nothing stopping a user from using a direct map
entry that's a multi-mount without an actual mount at its root.
So there could be directories created under these, it's just not
usually done.

I'm pretty sure I don't check and disallow this.

Ian

  reply	other threads:[~2020-01-14  0:25 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-30  5:20 [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Aleksa Sarai
2019-12-30  5:20 ` [PATCH RFC 1/1] " Aleksa Sarai
2019-12-30  7:34   ` Linus Torvalds
2019-12-30  8:28     ` Aleksa Sarai
2020-01-08  4:39       ` Andy Lutomirski
2019-12-30  5:44 ` [PATCH RFC 0/1] " Al Viro
2019-12-30  5:49   ` Aleksa Sarai
2019-12-30  7:29     ` Aleksa Sarai
2019-12-30  7:53       ` Linus Torvalds
2019-12-30  8:32         ` Aleksa Sarai
2020-01-02  8:58           ` David Laight
2020-01-02  9:09             ` Aleksa Sarai
2020-01-01  0:43       ` Al Viro
2020-01-01  0:54         ` Al Viro
2020-01-01  3:08           ` Al Viro
2020-01-01 14:44             ` Aleksa Sarai
2020-01-01 23:40               ` Al Viro
2020-01-02  3:59                 ` Aleksa Sarai
2020-01-03  1:49                   ` Al Viro
2020-01-04  4:46                     ` Ian Kent
2020-01-08  3:13                     ` Al Viro
2020-01-08  3:54                       ` Linus Torvalds
2020-01-08 21:34                         ` Al Viro
2020-01-10  0:08                           ` Linus Torvalds
2020-01-10  4:15                             ` Al Viro
2020-01-10  5:03                               ` Linus Torvalds
2020-01-10  6:20                               ` Ian Kent
     [not found]                                 ` <979cf680b0fbdce515293a3449d564690cde6a3f.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org>
2020-01-12 21:33                                   ` Al Viro
2020-01-13  2:59                                     ` Ian Kent
2020-01-14  0:25                                       ` Ian Kent [this message]
2020-01-14  4:39                                         ` Al Viro
2020-01-14  5:01                                           ` Ian Kent
     [not found]                                             ` <d6cad1552171da1eb38c55d1d7b1ff45902b101f.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org>
2020-01-14  5:59                                               ` Ian Kent
2020-01-10 21:07                         ` Aleksa Sarai
2020-01-14  4:57                           ` Al Viro
2020-01-14  5:12                             ` Al Viro
     [not found]                             ` <20200114045733.GW8904-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2020-01-14 20:01                               ` Aleksa Sarai
2020-01-15 14:25                                 ` Al Viro
2020-01-15 14:29                                   ` Aleksa Sarai
2020-01-15 14:34                                     ` Aleksa Sarai
2020-01-15 14:48                                       ` Al Viro
     [not found]                                         ` <20200115144831.GJ8904-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2020-01-18 12:07                                           ` [PATCH v3 0/2] openat2: minor uapi cleanups Aleksa Sarai
2020-01-18 12:07                                             ` [PATCH v3 1/2] open: introduce openat2(2) syscall Aleksa Sarai
     [not found]                                             ` <20200118120800.16358-1-cyphar-gVpy/LI/lHzQT0dZR+AlfA@public.gmane.org>
2020-01-18 12:08                                               ` [PATCH v3 2/2] selftests: add openat2(2) selftests Aleksa Sarai
2020-01-18 15:28                                             ` [PATCH v3 0/2] openat2: minor uapi cleanups Al Viro
     [not found]                                               ` <20200118152833.GS8904-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2020-01-18 18:09                                                 ` Al Viro
     [not found]                                                   ` <20200118180941.GT8904-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2020-01-18 23:03                                                     ` Aleksa Sarai
2020-01-19  1:12                                                       ` Al Viro
2020-01-15 13:57                             ` [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Aleksa Sarai
2020-01-19  3:14                               ` [RFC][PATCHSET][CFT] pathwalk cleanups and fixes Al Viro
2020-01-19 14:33                                 ` Ian Kent
2020-01-10 23:19                     ` [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Al Viro
2020-01-13  1:48                       ` Ian Kent
2020-01-13  3:54                         ` Al Viro
2020-01-13  6:00                           ` Ian Kent
2020-01-13  6:03                             ` Ian Kent
2020-01-13 13:30                               ` Al Viro
     [not found]                                 ` <20200113133047.GR8904-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2020-01-14  7:25                                   ` Ian Kent
2020-01-14 12:17                                     ` Ian Kent
2020-01-04  5:52               ` Andy Lutomirski

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