From: Andy Lutomirski <luto@amacapital.net>
To: alan.christopher.jenkins@gmail.com
Cc: Al Viro <viro@zeniv.linux.org.uk>,
David Howells <dhowells@redhat.com>,
Linux API <linux-api@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Miklos Szeredi <mszeredi@redhat.com>
Subject: Re: [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #12]
Date: Sat, 13 Oct 2018 16:04:09 -0700 [thread overview]
Message-ID: <CALCETrWvEJHGWNXvOBcaFbX16pyBEqmNk4V+dBxX00OAS4OMng@mail.gmail.com> (raw)
In-Reply-To: <68a2107f-bf70-055b-86cf-1ba2ba9422bf@gmail.com>
On Sat, Oct 13, 2018 at 2:45 AM Alan Jenkins
<alan.christopher.jenkins@gmail.com> wrote:
>
> On 13/10/2018 07:11, Al Viro wrote:
> > On Fri, Oct 12, 2018 at 03:49:50PM +0100, Alan Jenkins wrote:
> >>> +SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags)
> >>> +{
> >>> + struct fs_context *fc;
> >>> + struct path target;
> >>> + unsigned int lookup_flags;
> >>> + int ret;
> >>> +
> >>> + if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN))
> >>> + return -EPERM;
> >>
> >> This seems to accept basically any mount. Specifically: are you sure it's
> >> OK to return a handle to a SB_NO_USER superblock?
> > Umm... As long as we don't try to do pathname resolution from its ->s_root,
> > shouldn't be a problem and I don't see anything that would do that. I might've
> > missed something, but...
>
> Sorry, I guess SB_NOUSER was the wrong word. I was trying find if
> anything stopped things like
>
> int memfd = memfd_create("foo", 0);
> int fsfd = fspick(memfd, "", FSPICK_EMPTY_PATH);
>
> fsconfig(fsfd, FSCONFIG_SET_FLAG, "ro", NULL, 0);
> fsconfig(fsfd, FSCONFIG_SET_STRING, "size", "100M", 0);
> fsconfig(fsfd, FSCONFIG_CMD_RECONFIGURE, NULL, NULL, 0);
>
> So far I'm getting -EBUSY if I try to apply the "ro", -EINVAL if I try
> to apply the "size=100M". But if I don't apply either, then
> FSCONFIG_CMD_RECONFIGURE succeeds.
>
> It seems worrying that it might let me set options on shm_mnt. Or at
> least letting me get as far as the -EBUSY check for the "ro" superblock
> flag.
>
> I'm not sure why I'm getting the -EINVAL setting the "size" option. But
> it would be much more reassuring if I was getting -EPERM :-).
>
I would argue that the filesystem associated with a memfd, and even
the fact that there *is* a filesystem, is none of user code's
business. So that fspick() call should return -EINVAL or similar.
next prev parent reply other threads:[~2018-10-14 6:43 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 16:30 [PATCH 00/34] VFS: Introduce filesystem context [ver #12] David Howells
2018-09-21 16:30 ` [PATCH 01/34] vfs: syscall: Add open_tree(2) to reference or clone a mount " David Howells
2018-10-21 16:41 ` Eric W. Biederman
2018-09-21 16:30 ` [PATCH 02/34] vfs: syscall: Add move_mount(2) to move mounts around " David Howells
2018-09-21 16:30 ` [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE_CLONE " David Howells
2018-10-05 18:24 ` Alan Jenkins
2018-10-07 10:48 ` Alan Jenkins
2018-10-07 19:20 ` Alan Jenkins
2018-10-10 12:36 ` David Howells
2018-10-12 14:22 ` Alan Jenkins
2018-10-12 14:54 ` David Howells
2018-10-12 14:57 ` Alan Jenkins
2018-10-11 9:17 ` David Howells
2018-10-11 11:48 ` Alan Jenkins
2018-10-11 13:10 ` David Howells
2018-10-11 12:14 ` David Howells
2018-10-11 12:23 ` Alan Jenkins
2018-10-11 15:33 ` David Howells
2018-10-11 18:38 ` Eric W. Biederman
2018-10-11 20:17 ` David Howells
2018-10-13 6:06 ` Al Viro
2018-10-17 17:45 ` Alan Jenkins
2018-10-18 20:09 ` David Howells
2018-10-18 20:58 ` David Howells
2018-10-19 11:57 ` David Howells
2018-10-19 13:37 ` David Howells
2018-10-19 17:35 ` Alan Jenkins
2018-10-19 21:35 ` David Howells
2018-10-19 21:40 ` David Howells
2018-10-19 22:36 ` David Howells
2018-10-20 5:25 ` Al Viro
2018-10-20 11:06 ` Alan Jenkins
2018-10-20 11:48 ` Al Viro
2018-10-20 12:26 ` Al Viro
2018-10-21 0:40 ` David Howells
2018-10-10 11:56 ` David Howells
2018-10-10 12:31 ` David Howells
2018-10-10 12:39 ` Alan Jenkins
2018-10-10 12:50 ` David Howells
2018-10-10 13:02 ` David Howells
2018-10-10 13:06 ` Alan Jenkins
2018-10-21 16:57 ` Eric W. Biederman
2018-10-23 11:19 ` Alan Jenkins
2018-10-23 16:22 ` Al Viro
2018-09-21 16:30 ` [PATCH 04/34] vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled " David Howells
2018-09-21 16:30 ` [PATCH 05/34] vfs: Introduce the basic header for the new mount API's filesystem context " David Howells
2018-09-21 16:30 ` [PATCH 06/34] vfs: Introduce logging functions " David Howells
2018-09-21 16:31 ` [PATCH 07/34] vfs: Add configuration parser helpers " David Howells
2019-03-14 7:46 ` Geert Uytterhoeven
2019-03-14 10:27 ` David Howells
2019-03-14 10:49 ` Geert Uytterhoeven
2018-09-21 16:31 ` [PATCH 08/34] vfs: Add LSM hooks for the new mount API " David Howells
2018-09-21 16:31 ` [PATCH 09/34] vfs: Put security flags into the fs_context struct " David Howells
2018-09-21 16:31 ` [PATCH 10/34] selinux: Implement the new mount API LSM hooks " David Howells
2018-09-21 16:31 ` [PATCH 11/34] smack: Implement filesystem context security " David Howells
2018-09-21 16:31 ` [PATCH 12/34] apparmor: Implement security hooks for the new mount API " David Howells
2018-09-21 16:31 ` [PATCH 13/34] tomoyo: " David Howells
2018-09-21 16:32 ` [PATCH 14/34] vfs: Separate changing mount flags full remount " David Howells
2018-09-21 16:32 ` [PATCH 15/34] vfs: Implement a filesystem superblock creation/configuration context " David Howells
2018-09-21 16:32 ` [PATCH 16/34] vfs: Remove unused code after filesystem context changes " David Howells
2018-09-21 16:32 ` [PATCH 17/34] procfs: Move proc_fill_super() to fs/proc/root.c " David Howells
2018-09-21 16:32 ` [PATCH 18/34] proc: Add fs_context support to procfs " David Howells
2018-09-21 16:32 ` [PATCH 19/34] ipc: Convert mqueue fs to fs_context " David Howells
2018-09-21 16:32 ` [PATCH 20/34] cpuset: Use " David Howells
2018-09-21 16:33 ` [PATCH 21/34] kernfs, sysfs, cgroup, intel_rdt: Support " David Howells
2018-11-19 4:23 ` Andrei Vagin
2018-12-06 17:08 ` Andrei Vagin
2018-09-21 16:33 ` [PATCH 22/34] hugetlbfs: Convert to " David Howells
2018-09-21 16:33 ` [PATCH 23/34] vfs: Remove kern_mount_data() " David Howells
2018-09-21 16:33 ` [PATCH 24/34] vfs: Provide documentation for new mount API " David Howells
2018-09-21 16:33 ` [PATCH 25/34] Make anon_inodes unconditional " David Howells
2018-09-21 16:33 ` [PATCH 26/34] vfs: syscall: Add fsopen() to prepare for superblock creation " David Howells
2018-09-21 16:33 ` [PATCH 27/34] vfs: Implement logging through fs_context " David Howells
2018-09-21 16:33 ` [PATCH 28/34] vfs: Add some logging to the core users of the fs_context log " David Howells
2018-09-21 16:34 ` [PATCH 29/34] vfs: syscall: Add fsconfig() for configuring and managing a context " David Howells
2018-09-21 16:34 ` [PATCH 30/34] vfs: syscall: Add fsmount() to create a mount for a superblock " David Howells
2018-09-21 16:34 ` [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration " David Howells
2018-10-12 14:49 ` Alan Jenkins
2018-10-13 6:11 ` Al Viro
2018-10-13 9:45 ` Alan Jenkins
2018-10-13 23:04 ` Andy Lutomirski [this message]
2018-10-17 13:15 ` David Howells
2018-10-17 13:20 ` David Howells
2018-10-17 14:31 ` Alan Jenkins
2018-10-17 14:35 ` Eric W. Biederman
2018-10-17 14:55 ` Alan Jenkins
2018-10-17 15:24 ` David Howells
2018-10-17 15:38 ` Eric W. Biederman
2018-10-17 15:45 ` David Howells
2018-10-17 17:41 ` Alan Jenkins
2018-10-17 21:20 ` David Howells
2018-10-17 22:13 ` Alan Jenkins
2018-09-21 16:34 ` [PATCH 32/34] afs: Add fs_context support " David Howells
2018-09-21 16:34 ` [PATCH 33/34] afs: Use fs_context to pass parameters over automount " David Howells
2018-09-21 16:34 ` [PATCH 34/34] vfs: Add a sample program for the new mount API " David Howells
2018-12-17 14:12 ` Anders Roxell
2018-12-20 16:36 ` David Howells
2018-10-04 18:37 ` [PATCH 00/34] VFS: Introduce filesystem context " Eric W. Biederman
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