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Thu, 28 Jun 2018 05:50:18 +0000 Date: Wed, 27 Jun 2018 22:50:04 -0700 From: Andrei Vagin To: David Howells Cc: viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org Subject: Re: [12/24] proc: Add fs_context support to procfs [ver #7] Message-ID: <20180628055003.GA15563@outlook.office365.com> References: <20180626072736.GA31860@outlook.office365.com> <152414474815.23902.6952548431423168966.stgit@warthog.procyon.org.uk> <20180619033450.GA11639@outlook.office365.com> <20180626061320.GA12548@outlook.office365.com> <31831.1530003427@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="EVF5PPMfhYS0aIcm" Content-Disposition: inline In-Reply-To: <31831.1530003427@warthog.procyon.org.uk> User-Agent: Mutt/1.9.3 (2018-01-21) X-Originating-IP: [73.140.212.29] X-ClientProxiedBy: MWHPR17CA0052.namprd17.prod.outlook.com (2603:10b6:300:93::14) To AM6PR08MB3255.eurprd08.prod.outlook.com (2603:10a6:209:47::20) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 159b8ea6-a85e-4ad5-ea48-08d5dcbb0885 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652034)(8989117)(4534165)(4627221)(201703031133081)(201702281549075)(8990107)(5600026)(711020)(2017052603328)(7153060)(49563074)(7193020);SRVR:AM6PR08MB3255; 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charset=koi8-r Content-Disposition: inline On Tue, Jun 26, 2018 at 09:57:07AM +0100, David Howells wrote: > Andrei Vagin wrote: > > > > > > - mnt = kern_mount_data(&proc_fs_type, ns, 0); > > > > > > Here ns->user_ns and get_current_cred()->user_ns are not always equal > > > > What do you think about the attached patch? > > ... > > - fc = vfs_new_fs_context(&proc_fs_type, NULL, 0, > > - FS_CONTEXT_FOR_KERNEL_MOUNT); > > + fc = vfs_new_fs_context_userns(&proc_fs_type, NULL, 0, > > + FS_CONTEXT_FOR_KERNEL_MOUNT, ns->user_ns); > > Or you could just change fc->user_ns immediately after calling > vfs_new_fs_context(). This is what network filesystems should do with > fc->net_ns, for example. Ok, it works for me. The patch is attached. > > > -struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type, > > +struct fs_context *vfs_new_fs_context_userns(struct file_system_type *fs_type, > > struct dentry *reference, > > unsigned int sb_flags, > > - enum fs_context_purpose purpose) > > + enum fs_context_purpose purpose, > > + struct user_namespace *user_ns) > > > If you'd really rather add a new parameter, please don't rename the function > to vfs_new_fs_context_userns() - just add a new parameter. There don't need > to be two versions of it. > > > This brings me to another thought: I want to add the ability to let > namespaces be configured by userspace, for example: It may be a good feature, but I am not sure about procfs. A procfs instance is created per pidns, so they should have the same owner userns. > > fd = fsopen("nfs"); > sprintf(buf, "ns user %d", my_user_ns_fd); > write(fd, buf); > sprintf(buf, "ns net %d", my_net_ns_fd); > write(fd, buf); > write(fd, "s fedoraproject.org:/pub"); > write(fd, "o intr"); > ... > > I think therefore, I might need to insert another phase between creating the > context and calling the filesystem initialiser: > > fc = vfs_new_fs_context(&afs_fs_type, mntpt, 0, > FS_CONTEXT_FOR_SUBMOUNT); > > followed by: > > vfs_sb_set_namespace(fc, THIS_IS_USER_NS, user_ns); > vfs_sb_set_namespace(fc, THIS_IS_NET_NS, net_ns); > > but then we'd need to do: > > vfs_begin_options(fc); > > before continuing (unless we made this happen automatically on the receipt of > the first option): > > afs_mntpt_set_params(fc, mntpt); > vfs_get_tree(fc); > mnt = vfs_create_mount(fc, 0); > > Alternatively, we could do the namespace setting after initialisation and let > the fs apply the changes itself. > > David --EVF5PPMfhYS0aIcm Content-Type: text/plain; charset=koi8-r Content-Disposition: attachment; filename="0001-proc-set-a-proper-user-namespace-for-fs_context.patch" >From 2297ffb333a7bcee466a5273a3fc84202b9695a6 Mon Sep 17 00:00:00 2001 From: Andrei Vagin Date: Wed, 27 Jun 2018 22:45:43 -0700 Subject: [PATCH] proc: set a proper user namespace for fs_context A user namespace should be taken from a pidns for which a procfs is created. Signed-off-by: Andrei Vagin --- fs/proc/root.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/proc/root.c b/fs/proc/root.c index efbdc08a3c86..59aaf06a40c7 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -303,6 +303,11 @@ int pid_ns_prepare_proc(struct pid_namespace *ns) if (IS_ERR(fc)) return PTR_ERR(fc); + if (fc->user_ns != ns->user_ns) { + put_user_ns(fc->user_ns); + fc->user_ns = get_user_ns(ns->user_ns); + } + ctx = fc->fs_private; if (ctx->pid_ns != ns) { put_pid_ns(ctx->pid_ns); -- 2.17.0 --EVF5PPMfhYS0aIcm--