From: ebiederm@xmission.com (Eric W. Biederman)
To: Linux Containers <containers@lists.linux-foundation.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
<linux-kernel@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>
Subject: [PATCH review 4/6] userns: Allow the userns root to mount of devpts
Date: Fri, 25 Jan 2013 18:23:12 -0800 [thread overview]
Message-ID: <87obgchecv.fsf@xmission.com> (raw)
In-Reply-To: <87ehh8it9s.fsf@xmission.com> (Eric W. Biederman's message of "Fri, 25 Jan 2013 18:15:43 -0800")
- The context in which devpts is mounted has no effect on the creation
of ptys as the /dev/ptmx interface has been used by unprivileged
users for many years.
- Only support unprivileged mounts in combination with the newinstance
option to ensure that mounting of /dev/pts in a user namespace will
not allow the options of an existing mount of devpts to be modified.
- Create /dev/pts/ptmx as the root user in the user namespace that
mounts devpts so that it's permissions to be changed.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
fs/devpts/inode.c | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index 472e6be..073d30b 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -243,6 +243,13 @@ static int mknod_ptmx(struct super_block *sb)
struct dentry *root = sb->s_root;
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
+ kuid_t root_uid;
+ kgid_t root_gid;
+
+ root_uid = make_kuid(current_user_ns(), 0);
+ root_gid = make_kgid(current_user_ns(), 0);
+ if (!uid_valid(root_uid) || !gid_valid(root_gid))
+ return -EINVAL;
mutex_lock(&root->d_inode->i_mutex);
@@ -273,6 +280,8 @@ static int mknod_ptmx(struct super_block *sb)
mode = S_IFCHR|opts->ptmxmode;
init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+ inode->i_uid = root_uid;
+ inode->i_gid = root_gid;
d_add(dentry, inode);
@@ -438,6 +447,12 @@ static struct dentry *devpts_mount(struct file_system_type *fs_type,
if (error)
return ERR_PTR(error);
+ /* Require newinstance for all user namespace mounts to ensure
+ * the mount options are not changed.
+ */
+ if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
+ return ERR_PTR(-EINVAL);
+
if (opts.newinstance)
s = sget(fs_type, NULL, set_anon_super, flags, NULL);
else
@@ -491,6 +506,9 @@ static struct file_system_type devpts_fs_type = {
.name = "devpts",
.mount = devpts_mount,
.kill_sb = devpts_kill_sb,
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ .fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
+#endif
};
/*
--
1.7.5.4
next prev parent reply other threads:[~2013-01-26 2:23 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-26 2:15 [PATCH review 0/6] miscelaneous user namespace patches Eric W. Biederman
2013-01-26 2:19 ` [PATCH review 1/6] userns: Avoid recursion in put_user_ns Eric W. Biederman
2013-01-26 20:58 ` Serge E. Hallyn
2013-01-28 14:51 ` Vasily Kulikov
2013-01-28 16:34 ` Eric W. Biederman
2013-01-26 2:21 ` [PATCH review 2/6] userns: Allow any uid or gid mappings that don't overlap Eric W. Biederman
2013-01-26 21:08 ` Serge E. Hallyn
2013-01-28 14:28 ` Aristeu Rozanski
2013-01-28 14:41 ` Lord Glauber Costa of Sealand
2013-01-28 15:12 ` Aristeu Rozanski
2013-01-26 2:22 ` [PATCH review 3/6] userns: Recommend use of memory control groups Eric W. Biederman
2013-01-26 21:13 ` Serge E. Hallyn
2013-01-27 6:19 ` Eric W. Biederman
2013-01-28 7:37 ` Lord Glauber Costa of Sealand
2013-01-28 7:50 ` Lord Glauber Costa of Sealand
2013-01-28 8:14 ` Eric W. Biederman
2013-01-28 8:22 ` Lord Glauber Costa of Sealand
2013-01-28 16:19 ` Eric W. Biederman
2013-01-28 16:37 ` Lord Glauber Costa of Sealand
2013-01-28 17:18 ` Eric W. Biederman
2013-01-28 8:05 ` Eric W. Biederman
2013-01-26 2:23 ` Eric W. Biederman [this message]
2013-01-26 21:22 ` [PATCH review 4/6] userns: Allow the userns root to mount of devpts Serge E. Hallyn
2013-01-26 2:26 ` [PATCH review 5/6] userns: Allow the userns root to mount ramfs Eric W. Biederman
2013-01-26 21:29 ` Serge E. Hallyn
2013-01-27 6:09 ` Eric W. Biederman
2013-01-27 18:23 ` Serge E. Hallyn
2013-01-27 18:23 ` Serge E. Hallyn
2013-01-26 2:26 ` [PATCH review 6/6] userns: Allow the userns root to mount tmpfs Eric W. Biederman
2013-01-27 18:23 ` Serge E. Hallyn
2013-01-28 1:28 ` Gao feng
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