From: Alan Jenkins <alan.christopher.jenkins@gmail.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>,
linux-api@vger.kernel.org, torvalds@linux-foundation.org,
ebiederm@xmission.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, 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 10:45:01 +0100 [thread overview]
Message-ID: <68a2107f-bf70-055b-86cf-1ba2ba9422bf@gmail.com> (raw)
In-Reply-To: <20181013061141.GR32577@ZenIV.linux.org.uk>
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 :-).
Alan
next prev parent reply other threads:[~2018-10-13 9:45 UTC|newest]
Thread overview: 24+ 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 16:33 ` [PATCH 26/34] vfs: syscall: Add fsopen() to prepare for superblock creation " 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 [this message]
2018-10-13 23:04 ` Andy Lutomirski
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
2018-10-04 18:37 ` [PATCH 00/34] VFS: Introduce filesystem context " Eric W. Biederman
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