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From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
	Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Rob Landley <rob@landley.net>
Subject: Re: [RFC][PATCH 0/3] vfs: Detach mounts on unlink.
Date: Fri, 4 Oct 2013 16:20:10 -0700	[thread overview]
Message-ID: <CA+55aFyCDyGqqbueJtZSUh5JeMcGONy+nW=RXiiouneXuxQ9aA@mail.gmail.com> (raw)
In-Reply-To: <87li281wx6.fsf_-_@xmission.com>

On Fri, Oct 4, 2013 at 3:41 PM, Eric W. Biederman <ebiederm@xmission.com> wrote:
>
> After thinking about it removing the restrictions on mount points
> appears safe, because it is just plain dumb to have a mount point
> in a directory that is not restricted to root only modifications.
>
> This is a change in user visible semantics, so I want to be very careful
> about this.  Are there any reasons to not make this change?

At least one worry: people are very used to 'rmdir()' not removing
empty directories, and I've written code myself that just does an
'rmdir()' without worrying about it. I think git has code like "remove
file, then try to remove directory file is in, and recurse until it
fails or you hit the top of tree". And it all depends on knowing that
rmdir() is harmless, and returns the appropriate error when the
directory isn't empty.

And you're now changing that. If it's a mount-point, the rmdir just
succeeds, afaik.

Does anybody care? I dunno. But it looks like a _big_ semantic change.

That said, I like the _concept_ of being able to remove a mount-point
and the mount just goes away. But I do think that for sanity sake, it
should have something like "if one of the mounts is in the current
namespace, return -EBUSY". IOW, the patch-series would make the VFS
layer _able_ to remove mount-points, but a normal rmdir() when
something is mounted in that namespace would fail in order to give
legacy behavior.

Hmm?

                Linus

  parent reply	other threads:[~2013-10-04 23:20 UTC|newest]

Thread overview: 181+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-08-14 17:42 DoS with unprivileged mounts Miklos Szeredi
2013-08-14 19:26 ` Andy Lutomirski
2013-08-14 19:53   ` Eric W. Biederman
2013-08-14 20:25     ` Andy Lutomirski
2013-08-14 21:54       ` Eric W. Biederman
2013-08-14 19:32 ` Eric W. Biederman
2013-08-15  4:59   ` Miklos Szeredi
2013-08-15  6:45     ` Eric W. Biederman
2013-08-15  6:52       ` Andy Lutomirski
2013-08-15  7:55         ` Eric W. Biederman
2013-08-15  9:29       ` Miklos Szeredi
2013-10-04 22:41         ` [RFC][PATCH 0/3] vfs: Detach mounts on unlink Eric W. Biederman
2013-10-04 22:42           ` [RFC][PATCH 1/3] vfs: Keep a list of mounts on a mount point Eric W. Biederman
2013-10-08 13:44             ` Miklos Szeredi
2013-10-08 20:31               ` Eric W. Biederman
2013-10-04 22:43           ` [RFC][PATCH 2/3] vfs: Add a function to lazily unmount all mounts from any dentry Eric W. Biederman
2013-10-07  4:22             ` Serge E. Hallyn
2013-10-07  6:15               ` Eric W. Biederman
2013-10-08 13:56             ` Miklos Szeredi
2013-10-08 20:32               ` Eric W. Biederman
2013-10-04 22:43           ` [RFC][PATCH 3/3] vfs: Lazily remove mounts on unlinked files and directories Eric W. Biederman
2013-10-08 15:50             ` Miklos Szeredi
2013-10-08 21:47               ` Eric W. Biederman
2013-10-09 19:12                 ` Grrrr fusermount Eric W. Biederman
2013-10-09 20:09                   ` Andy Lutomirski
2013-10-09 23:35                     ` Eric W. Biederman
2013-10-04 23:20           ` Linus Torvalds [this message]
2013-10-05  0:03             ` [RFC][PATCH 0/3] vfs: Detach mounts on unlink Eric W. Biederman
2013-10-05  1:57               ` Eric W. Biederman
2013-10-05 23:42               ` Rob Landley
2013-10-06  0:44                 ` Eric W. Biederman
2013-10-08  8:03                 ` Karel Zak
2013-10-10  6:46                   ` Rob Landley
2013-10-05  2:34           ` [RFC][PATCH 4/3] vfs: Allow rmdir to remove mounts in all but the current mount namespace Eric W. Biederman
2013-10-05 15:44             ` Serge E. Hallyn
2013-10-07  4:39             ` Serge E. Hallyn
2013-10-07  6:55               ` Eric W. Biederman
2013-10-07 16:53                 ` Andy Lutomirski
2013-10-07 22:25                   ` Eric W. Biederman
2013-10-08 16:06                     ` Miklos Szeredi
2013-10-08 16:06                       ` Andy Lutomirski
2013-10-08 16:11                         ` Miklos Szeredi
2013-10-08 20:50                           ` Eric W. Biederman
2013-10-10 10:02                             ` Miklos Szeredi
2013-10-10 11:43                               ` Eric W. Biederman
2013-10-10 11:57                                 ` Miklos Szeredi
2013-10-12  1:04                                   ` Eric W. Biederman
2013-10-12  1:39                                     ` Eric W. Biederman
     [not found]                                       ` <87d2nb8dxy.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-10-15 20:15                                         ` [REVIEW][PATCH 0/4] vfs: Detach mounts on unlink Eric W. Biederman
2013-10-15 20:15                                           ` Eric W. Biederman
2013-10-15 20:16                                           ` [REVIEW][PATCH 1/4] vfs: Don't allow overwriting mounts in the current mount namespace Eric W. Biederman
2013-11-03  3:54                                             ` Al Viro
     [not found]                                               ` <20131103035406.GA8537-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2013-11-08 20:51                                                 ` Eric W. Biederman
2013-11-08 20:51                                                   ` Eric W. Biederman
2013-11-08 21:35                                                   ` Al Viro
     [not found]                                                     ` <20131108213551.GR13318-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2013-11-08 22:17                                                       ` Eric W. Biederman
2013-11-08 22:17                                                         ` Eric W. Biederman
     [not found]                                                         ` <87fvr61qtg.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-11-09  8:49                                                           ` Christoph Hellwig
2013-11-09  8:49                                                             ` Christoph Hellwig
     [not found]                                                             ` <20131109084916.GA21413-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2013-11-21 20:58                                                               ` Eric W. Biederman
2013-11-21 20:58                                                                 ` Eric W. Biederman
     [not found]                                                   ` <87bo1u8vmf.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-11-08 21:35                                                     ` Al Viro
2013-11-21 20:49                                                 ` Eric W. Biederman
2013-11-21 20:49                                                   ` Eric W. Biederman
     [not found]                                             ` <87d2n6xpan.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-10-22 19:04                                               ` Serge E. Hallyn
2013-10-22 19:04                                                 ` Serge E. Hallyn
2013-11-03  3:54                                               ` Al Viro
     [not found]                                           ` <87iowyxpci.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-10-15 20:16                                             ` Eric W. Biederman
2013-10-15 20:17                                             ` [REVIEW][PATCH 2/4] vfs: Keep a list of mounts on a mount point Eric W. Biederman
2013-10-15 20:17                                               ` Eric W. Biederman
     [not found]                                               ` <877gdexp9s.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-10-22 19:06                                                 ` Serge E. Hallyn
2013-10-22 19:06                                                   ` Serge E. Hallyn
2013-10-15 20:17                                             ` [REVIEW][PATCH 3/4] vfs: Add a function to lazily unmount all mounts from any dentry. v3 Eric W. Biederman
2013-10-15 20:17                                               ` Eric W. Biederman
     [not found]                                               ` <871u3mxp8s.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-10-22 19:08                                                 ` Serge E. Hallyn
2013-10-22 19:08                                                   ` Serge E. Hallyn
2013-10-15 20:18                                             ` [REVIEW][PATCH 4/4] vfs: Lazily remove mounts on unlinked files and directories. v2 Eric W. Biederman
2013-10-15 20:18                                               ` Eric W. Biederman
     [not found]                                               ` <87vc0ywan7.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2013-10-22 19:13                                                 ` Serge E. Hallyn
2013-10-22 19:13                                                   ` Serge E. Hallyn
2013-10-08 10:42                 ` [RFC][PATCH 4/3] vfs: Allow rmdir to remove mounts in all but the current mount namespace Matthias Schniedermeyer
2013-10-08 13:13                   ` Eric W. Biederman
2013-10-05 23:07           ` [RFC][PATCH 0/3] vfs: Detach mounts on unlink Rob Landley
2013-10-05 23:17             ` Linus Torvalds
2013-10-05 23:22               ` Linus Torvalds
2013-10-06  0:18                 ` Rob Landley
2013-10-06  0:37                   ` Linus Torvalds
2013-10-05 23:24               ` Al Viro
2013-10-06  0:22                 ` Rob Landley
2013-10-06  0:12               ` Rob Landley
2013-10-05 23:19             ` Al Viro
2013-10-06  0:13               ` Rob Landley
2014-02-15 21:34           ` [PATCH 0/11] Detaching " Eric W. Biederman
2014-02-15 21:35             ` [PATCH 01/11] vfs: Document the effect of d_revalidate on d_find_alias Eric W. Biederman
2014-02-15 21:36             ` [PATCH 02/11] vfs: More precise tests in d_invalidate Eric W. Biederman
2014-02-15 22:51               ` Linus Torvalds
2014-02-15 22:59                 ` Linus Torvalds
2014-02-15 23:23                   ` Eric W. Biederman
2014-02-15 23:39                     ` Eric W. Biederman
2014-02-16  0:03                     ` Linus Torvalds
2014-02-16  1:22                       ` Eric W. Biederman
2014-02-15 21:36             ` [PATCH 03/11] vfs: Don't allow overwriting mounts in the current mount namespace Eric W. Biederman
2014-02-18 17:12               ` Miklos Szeredi
2014-02-18 21:28                 ` Eric W. Biederman
2014-02-18 22:20                   ` Linus Torvalds
2014-02-19  2:23                     ` Stephen Rothwell
2014-02-24 23:43                       ` Eric W. Biederman
2014-02-15 21:37             ` [PATCH 04/11] vfs: Keep a list of mounts on a mount point Eric W. Biederman
2014-02-15 21:37             ` [PATCH 05/11] vfs: Add a function to lazily unmount all mounts from any dentry Eric W. Biederman
2014-02-16  1:50               ` Eric W. Biederman
2014-02-18 17:17               ` Miklos Szeredi
2014-02-25  3:24                 ` Eric W. Biederman
2014-02-15 21:38             ` [PATCH 06/11] vfs: Lazily remove mounts on unlinked files and directories Eric W. Biederman
2014-02-15 21:38             ` [PATCH 07/11] vfs: Remove unnecessary calls of check_submounts_and_drop Eric W. Biederman
2014-02-15 21:39             ` [PATCH 08/11] vfs: Merge check_submounts_and_drop and d_invalidate Eric W. Biederman
2014-02-18 17:40               ` Miklos Szeredi
2014-02-25  0:01                 ` Eric W. Biederman
2014-02-25 15:13                   ` J. Bruce Fields
2014-02-25 22:03                     ` Eric W. Biederman
2014-02-26 19:37                       ` J. Bruce Fields
2014-02-27  2:05                         ` Eric W. Biederman
2014-02-15 21:39             ` [PATCH 09/11] vfs: Make d_invalidate return void Eric W. Biederman
2014-02-15 21:40             ` [PATCH 10/11] vfs: Remove d_drop calls from d_revalidate implementations Eric W. Biederman
2014-02-15 21:40             ` [PATCH 11/11] proc: Update proc_flush_task_mnt to use d_invalidate Eric W. Biederman
2014-02-18 17:43             ` [PATCH 0/11] Detaching mounts on unlink Miklos Szeredi
2014-02-25  9:33             ` [PATCH 0/12] Detaching mounts on unlink (for 3.15 v2) Eric W. Biederman
2014-02-25  9:34               ` [PATCH 01/12] vfs: Document the effect of d_revalidate on d_find_alias Eric W. Biederman
2014-02-25  9:35               ` [PATCH 02/12] vfs: More precise tests in d_invalidate Eric W. Biederman
2014-02-25  9:35               ` [PATCH 03/12] vfs: Don't allow overwriting mounts in the current mount namespace Eric W. Biederman
2014-02-25  9:36               ` [PATCH 04/12] vfs: Keep a list of mounts on a mount point Eric W. Biederman
2014-02-25  9:37               ` [PATCH 05/12] vfs: factor out lookup_mountpoint from new_mountpoint Eric W. Biederman
2014-02-25  9:38               ` [PATCH 06/12] vfs: Add a function to lazily unmount all mounts from any dentry Eric W. Biederman
2014-02-25  9:38               ` [PATCH 07/12] vfs: Lazily remove mounts on unlinked files and directories Eric W. Biederman
2014-02-25  9:39               ` [PATCH 08/12] vfs: Remove unnecessary calls of check_submounts_and_drop Eric W. Biederman
2014-02-25  9:40               ` [PATCH 09/12] vfs: Merge check_submounts_and_drop and d_invalidate Eric W. Biederman
2014-02-25  9:40               ` [PATCH 10/12] vfs: Make d_invalidate return void Eric W. Biederman
2014-02-25  9:41               ` [PATCH 11/12] vfs: Remove d_drop calls from d_revalidate implementations Eric W. Biederman
2014-02-25  9:41               ` [PATCH 12/12] proc: Update proc_flush_task_mnt to use d_invalidate Eric W. Biederman
2014-04-09  0:21               ` [GIT PULL] Detaching mounts on unlink for 3.15-rc1 Eric W. Biederman
2014-04-09  2:30                 ` Al Viro
2014-04-09  2:39                   ` Al Viro
2014-04-09  9:02                     ` Eric W. Biederman
2014-04-09 17:32                     ` Eric W. Biederman
2014-04-09 17:53                       ` Al Viro
2014-04-09 18:28                         ` Al Viro
2014-04-09 22:49                           ` Eric W. Biederman
2014-04-09 22:58                             ` [RFC][PATCH] vfs: In mntput run deactivate_super on a shallow stack Eric W. Biederman
2014-04-09 23:24                               ` Al Viro
2014-04-10  1:36                                 ` Eric W. Biederman
2014-04-12 22:15                                 ` Eric W. Biederman
2014-04-13  5:39                                   ` Al Viro
2014-04-13  5:49                                     ` Al Viro
2014-04-13  7:01                                     ` Eric W. Biederman
2014-04-13  7:51                                       ` Eric W. Biederman
2014-04-13 21:52                                         ` Al Viro
2014-04-14  7:38                                           ` [RFC][PATCH 0/4] No I/O from mntput Eric W. Biederman
2014-04-14  7:40                                             ` [PATCH 1/4] vfs: Remove useless loop in mntput_no_expire Eric W. Biederman
2014-04-14  7:40                                             ` [PATCH 2/4] vfs: Move autoclose of BSD accounting into a work queue Eric W. Biederman
2014-04-14  7:41                                             ` [PATCH 3/4] vfs: In mntput run deactivate_super on a shallow stack Eric W. Biederman
2014-04-14  7:42                                             ` [PATCH 4/4] vfs: Block intuitively in the case of BSD accounting files Eric W. Biederman
2014-04-16 22:03                                             ` [RFC][PATCH 0/4] No I/O from mntput Eric W. Biederman
2014-04-17 20:05                                               ` [GIT PULL] Detaching mounts on unlink for 3.15 Eric W. Biederman
2014-04-17 20:22                                                 ` Al Viro
2014-04-17 21:23                                                   ` Eric W. Biederman
2014-04-17 22:12                                                     ` Al Viro
2014-04-17 22:14                                                       ` Al Viro
2014-04-18  0:37                                                       ` Al Viro
2014-04-18  0:58                                                         ` Al Viro
2014-04-19  1:35                                                         ` Al Viro
2014-04-19  2:16                                                           ` Al Viro
2014-04-19  7:05                                                             ` Al Viro
2014-04-20  5:41                                                       ` Al Viro
2014-05-11 16:45                                                         ` Al Viro
2014-05-11 17:05                                                           ` Al Viro
2014-08-09  9:34                                                           ` Al Viro
2014-08-09  9:55                                                             ` Eric W. Biederman
2014-08-12 10:17                                                             ` Eric W. Biederman
2014-08-13 13:18                                                               ` Al Viro
2014-08-13 17:18                                                                 ` Eric W. Biederman
2014-04-09 22:01                       ` [GIT PULL] Detaching mounts on unlink for 3.15-rc1 Dave Chinner
2013-08-15 21:23 ` DoS with unprivileged mounts Rob Landley

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