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From: Andy Lutomirski <luto@kernel.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	David Howells <dhowells@redhat.com>,
	Linux API <linux-api@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Jann Horn <jannh@google.com>
Subject: Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9]
Date: Tue, 10 Jul 2018 18:33:16 -0700	[thread overview]
Message-ID: <CALCETrXWZJfBq-HnQ0vnGUBsDW75d4XFp1aQfTSqrFobQtFfbQ@mail.gmail.com> (raw)
In-Reply-To: <20180711011520.GL30522@ZenIV.linux.org.uk>

On Tue, Jul 10, 2018 at 6:15 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Tue, Jul 10, 2018 at 06:05:49PM -0700, Linus Torvalds wrote:
>> Yeah, Andy is right that we should *not* make "write()" have side effects.
>>
>> Use it to queue things by all means, but not "do" things. Not unless
>> there's a very sane security model.
>>
>> On Tue, Jul 10, 2018 at 4:59 PM Andy Lutomirski <luto@amacapital.net> wrote:
>> >
>> > I think the right solution is one of:
>> >
>> > (a) Pass a netlink-formatted blob to fsopen() and do the whole thing in one syscall. I don’t mean using netlink sockets — just the nlattr format.  Or you could use a different format. The part that matters is using just one syscall to do the whole thing.
>>
>> Please no. Not another nasty marshalling thing.
>>
>> > (b) Keep the current structure but use a new syscall instead of write().
>> >
>> > (c) Keep using write() but literally just buffer the data. Then have a new syscall to commit it.  In other words, replace “x” with a syscall and call all the fs_context_operations helpers in that context instead of from write().
>>
>> But yeah, b-or-c sounds fine.
>
> Umm...  How about "use credentials of opener for everything"?

If you want to audit every single filesystem for any code that uses
credentials for anything and add all the right kernel APIs and make
sure the filesystem uses them and somehow keep screwups from getting
added down the line, then okay I guess.  As far as I know, we don't
even *have* an API for "open this device node using this struct cred
*".

I kind of want to add a hack to set some poison bit in current->cred
in sys_write() and clear it on the way out.  Sigh.

--Andy

  reply	other threads:[~2018-07-11  1:35 UTC|newest]

Thread overview: 113+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-10 22:41 [PATCH 00/32] VFS: Introduce filesystem context [ver #9] David Howells
2018-07-10 22:41 ` [PATCH 01/32] vfs: syscall: Add open_tree(2) to reference or clone a mount " David Howells
2018-07-10 22:41 ` [PATCH 02/32] vfs: syscall: Add move_mount(2) to move mounts around " David Howells
2018-07-10 22:41 ` [PATCH 03/32] teach move_mount(2) to work with OPEN_TREE_CLONE " David Howells
2018-07-10 22:41 ` [PATCH 04/32] vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled " David Howells
2018-07-10 22:42 ` [PATCH 05/32] vfs: Introduce the basic header for the new mount API's filesystem context " David Howells
2018-07-10 22:42 ` [PATCH 06/32] vfs: Add LSM hooks for the new mount API " David Howells
2018-07-10 22:42 ` [PATCH 07/32] selinux: Implement the new mount API LSM hooks " David Howells
2018-07-11 14:08   ` Stephen Smalley
2018-07-10 22:42 ` [PATCH 08/32] smack: Implement filesystem context security " David Howells
2018-07-10 23:13   ` Casey Schaufler
2018-07-10 23:19   ` David Howells
2018-07-10 23:28     ` Casey Schaufler
2018-07-10 22:42 ` [PATCH 09/32] apparmor: Implement security hooks for the new mount API " David Howells
2018-07-10 22:42 ` [PATCH 10/32] tomoyo: " David Howells
2018-07-10 23:34   ` Tetsuo Handa
2018-07-10 22:42 ` [PATCH 11/32] vfs: Require specification of size of mount data for internal mounts " David Howells
2018-07-10 22:51   ` Linus Torvalds
2018-07-10 22:42 ` [PATCH 12/32] vfs: Separate changing mount flags full remount " David Howells
2018-07-10 22:42 ` [PATCH 13/32] vfs: Implement a filesystem superblock creation/configuration context " David Howells
2018-07-10 22:43 ` [PATCH 14/32] vfs: Remove unused code after filesystem context changes " David Howells
2018-07-10 22:43 ` [PATCH 15/32] procfs: Move proc_fill_super() to fs/proc/root.c " David Howells
2018-07-10 22:43 ` [PATCH 16/32] proc: Add fs_context support to procfs " David Howells
2018-07-10 22:43 ` [PATCH 17/32] ipc: Convert mqueue fs to fs_context " David Howells
2018-07-10 22:43 ` [PATCH 18/32] cpuset: Use " David Howells
2018-07-10 22:43 ` [PATCH 19/32] kernfs, sysfs, cgroup, intel_rdt: Support " David Howells
2018-07-10 22:43 ` [PATCH 20/32] hugetlbfs: Convert to " David Howells
2018-07-10 22:43 ` [PATCH 21/32] vfs: Remove kern_mount_data() " David Howells
2018-07-10 22:43 ` [PATCH 22/32] vfs: Provide documentation for new mount API " David Howells
2018-07-13  1:37   ` Randy Dunlap
2018-07-13  9:45   ` David Howells
2018-07-10 22:44 ` [PATCH 23/32] Make anon_inodes unconditional " David Howells
2018-07-10 22:44 ` [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation " David Howells
2018-07-10 23:59   ` Andy Lutomirski
2018-07-11  1:05     ` Linus Torvalds
2018-07-11  1:15       ` Al Viro
2018-07-11  1:33         ` Andy Lutomirski [this message]
2018-07-11  1:48         ` Linus Torvalds
2018-07-11  8:43         ` David Howells
2018-07-11  1:14     ` Jann Horn
2018-07-11  1:16       ` Al Viro
2018-07-11  8:42     ` David Howells
2018-07-11 16:03       ` Linus Torvalds
2018-07-11  7:22   ` David Howells
2018-07-11 16:38     ` Eric Biggers
2018-07-11 17:06     ` Andy Lutomirski
2018-07-12 14:54     ` David Howells
2018-07-12 15:50       ` Linus Torvalds
2018-07-12 16:00         ` Al Viro
2018-07-12 16:07           ` Linus Torvalds
2018-07-12 16:31             ` Al Viro
2018-07-12 16:39               ` Linus Torvalds
2018-07-12 17:14                 ` Linus Torvalds
2018-07-12 17:44                   ` Al Viro
2018-07-12 17:54                     ` Linus Torvalds
2018-07-12 17:52                 ` Al Viro
2018-07-12 16:23       ` Andy Lutomirski
2018-07-12 16:31         ` Linus Torvalds
2018-07-12 16:41         ` Al Viro
2018-07-12 16:58         ` Al Viro
2018-07-12 17:54           ` Andy Lutomirski
2018-07-12 20:23       ` David Howells
2018-07-12 20:25         ` Andy Lutomirski
2018-07-12 20:34         ` Linus Torvalds
2018-07-12 20:36           ` Linus Torvalds
2018-07-12 21:26         ` David Howells
2018-07-12 21:40           ` Linus Torvalds
2018-07-12 22:32           ` Theodore Y. Ts'o
2018-07-12 22:54           ` David Howells
2018-07-12 23:21             ` Andy Lutomirski
2018-07-12 23:23             ` Jann Horn
2018-07-12 23:33               ` Jann Horn
2018-07-12 23:35             ` David Howells
2018-07-12 23:50               ` Andy Lutomirski
2018-07-13  0:03               ` David Howells
2018-07-13  0:24                 ` Andy Lutomirski
2018-07-13  7:30                 ` David Howells
2018-07-19  1:30                   ` Eric W. Biederman
2018-07-13  2:35             ` Theodore Y. Ts'o
2018-07-12 21:00       ` David Howells
2018-07-12 21:29         ` Linus Torvalds
2018-07-13 13:27         ` David Howells
2018-07-13 15:01           ` Andy Lutomirski
2018-07-13 15:40           ` David Howells
2018-07-13 17:14             ` Andy Lutomirski
2018-07-17  9:40           ` David Howells
2018-07-11 15:51   ` Jonathan Corbet
2018-07-11 16:18   ` David Howells
2018-07-12 17:15   ` Greg KH
2018-07-12 17:20     ` Al Viro
2018-07-12 18:03       ` Greg KH
2018-07-12 18:30         ` Andy Lutomirski
2018-07-12 18:34           ` Al Viro
2018-07-12 18:35             ` Al Viro
2018-07-12 19:08           ` Greg KH
2018-07-10 22:44 ` [PATCH 25/32] vfs: syscall: Add fsmount() to create a mount for a superblock " David Howells
2018-07-10 22:44 ` [PATCH 26/32] vfs: syscall: Add fspick() to select a superblock for reconfiguration " David Howells
2018-07-10 22:44 ` [PATCH 27/32] vfs: Implement logging through fs_context " David Howells
2018-07-10 22:44 ` [PATCH 28/32] vfs: Add some logging to the core users of the fs_context log " David Howells
2018-07-10 22:44 ` [PATCH 29/32] afs: Add fs_context support " David Howells
2018-07-10 22:44 ` [PATCH 30/32] afs: Use fs_context to pass parameters over automount " David Howells
2018-07-10 22:44 ` [PATCH 31/32] vfs: syscall: Add fsinfo() to query filesystem information " David Howells
2018-07-10 22:45 ` [PATCH 32/32] afs: Add fsinfo support " David Howells
2018-07-10 22:52 ` [MANPAGE PATCH] Add manpages for move_mount(2) and open_tree(2) David Howells
2019-10-09  9:51   ` Michael Kerrisk (man-pages)
2018-07-10 22:54 ` [MANPAGE PATCH] Add manpage for fsopen(2), fspick(2) and fsmount(2) David Howells
2019-10-09  9:52   ` Michael Kerrisk (man-pages)
2018-07-10 22:55 ` [MANPAGE PATCH] Add manpage for fsinfo(2) David Howells
2019-10-09  9:52   ` Michael Kerrisk (man-pages)
2019-10-09 12:02   ` David Howells
2018-07-10 23:01 ` [PATCH 00/32] VFS: Introduce filesystem context [ver #9] Linus Torvalds
2018-07-12  0:46 ` David Howells
2018-07-18 21:29 ` Getting rid of the usage of write() -- was " David Howells

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