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authorLinus Torvalds <torvalds@linux-foundation.org>2014-12-17 12:31:40 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-17 12:31:40 -0800
commit87c31b39abcb6fb6bd7d111200c9627a594bf6a9 (patch)
treeab2e5331fea9b823cb92719d0954a9141451c931 /fs
parentf045bbb9fa1bf6f507ad4de12d4e3471d8f672f1 (diff)
parentdb86da7cb76f797a1a8b445166a15cb922c6ff85 (diff)
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull user namespace related fixes from Eric Biederman: "As these are bug fixes almost all of thes changes are marked for backporting to stable. The first change (implicitly adding MNT_NODEV on remount) addresses a regression that was created when security issues with unprivileged remount were closed. I go on to update the remount test to make it easy to detect if this issue reoccurs. Then there are a handful of mount and umount related fixes. Then half of the changes deal with the a recently discovered design bug in the permission checks of gid_map. Unix since the beginning has allowed setting group permissions on files to less than the user and other permissions (aka ---rwx---rwx). As the unix permission checks stop as soon as a group matches, and setgroups allows setting groups that can not later be dropped, results in a situtation where it is possible to legitimately use a group to assign fewer privileges to a process. Which means dropping a group can increase a processes privileges. The fix I have adopted is that gid_map is now no longer writable without privilege unless the new file /proc/self/setgroups has been set to permanently disable setgroups. The bulk of user namespace using applications even the applications using applications using user namespaces without privilege remain unaffected by this change. Unfortunately this ix breaks a couple user space applications, that were relying on the problematic behavior (one of which was tools/selftests/mount/unprivileged-remount-test.c). To hopefully prevent needing a regression fix on top of my security fix I rounded folks who work with the container implementations mostly like to be affected and encouraged them to test the changes. > So far nothing broke on my libvirt-lxc test bed. :-) > Tested with openSUSE 13.2 and libvirt 1.2.9. > Tested-by: Richard Weinberger <richard@nod.at> > Tested on Fedora20 with libvirt 1.2.11, works fine. > Tested-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com> > Ok, thanks - yes, unprivileged lxc is working fine with your kernels. > Just to be sure I was testing the right thing I also tested using > my unprivileged nsexec testcases, and they failed on setgroup/setgid > as now expected, and succeeded there without your patches. > Tested-by: Serge Hallyn <serge.hallyn@ubuntu.com> > I tested this with Sandstorm. It breaks as is and it works if I add > the setgroups thing. > Tested-by: Andy Lutomirski <luto@amacapital.net> # breaks things as designed :(" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: userns: Unbreak the unprivileged remount tests userns; Correct the comment in map_write userns: Allow setting gid_maps without privilege when setgroups is disabled userns: Add a knob to disable setgroups on a per user namespace basis userns: Rename id_map_mutex to userns_state_mutex userns: Only allow the creator of the userns unprivileged mappings userns: Check euid no fsuid when establishing an unprivileged uid mapping userns: Don't allow unprivileged creation of gid mappings userns: Don't allow setgroups until a gid mapping has been setablished userns: Document what the invariant required for safe unprivileged mappings. groups: Consolidate the setgroups permission checks mnt: Clear mnt_expire during pivot_root mnt: Carefully set CL_UNPRIVILEGED in clone_mnt mnt: Move the clear of MNT_LOCKED from copy_tree to it's callers. umount: Do not allow unmounting rootfs. umount: Disallow unprivileged mount force mnt: Update unprivileged remount test mnt: Implicitly add MNT_NODEV on remount when it was implicitly added by mount
Diffstat (limited to 'fs')
-rw-r--r--fs/namespace.c18
-rw-r--r--fs/pnode.c1
-rw-r--r--fs/proc/base.c53
3 files changed, 69 insertions, 3 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 30df6e7dd807..820af6a1dd6b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -963,7 +963,8 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
}
/* Don't allow unprivileged users to reveal what is under a mount */
- if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
+ if ((flag & CL_UNPRIVILEGED) &&
+ (!(flag & CL_EXPIRE) || list_empty(&old->mnt_expire)))
mnt->mnt.mnt_flags |= MNT_LOCKED;
atomic_inc(&sb->s_active);
@@ -1544,6 +1545,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
goto dput_and_out;
if (mnt->mnt.mnt_flags & MNT_LOCKED)
goto dput_and_out;
+ retval = -EPERM;
+ if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
+ goto dput_and_out;
retval = do_umount(mnt, flags);
dput_and_out:
@@ -1606,7 +1610,6 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
if (IS_ERR(q))
return q;
- q->mnt.mnt_flags &= ~MNT_LOCKED;
q->mnt_mountpoint = mnt->mnt_mountpoint;
p = mnt;
@@ -2097,7 +2100,13 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
}
if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
!(mnt_flags & MNT_NODEV)) {
- return -EPERM;
+ /* Was the nodev implicitly added in mount? */
+ if ((mnt->mnt_ns->user_ns != &init_user_ns) &&
+ !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) {
+ mnt_flags |= MNT_NODEV;
+ } else {
+ return -EPERM;
+ }
}
if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
!(mnt_flags & MNT_NOSUID)) {
@@ -2958,6 +2967,8 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
/* mount new_root on / */
attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
touch_mnt_namespace(current->nsproxy->mnt_ns);
+ /* A moved mount should not expire automatically */
+ list_del_init(&new_mnt->mnt_expire);
unlock_mount_hash();
chroot_fs_refs(&root, &new);
put_mountpoint(root_mp);
@@ -3002,6 +3013,7 @@ static void __init init_mount_tree(void)
root.mnt = mnt;
root.dentry = mnt->mnt_root;
+ mnt->mnt_flags |= MNT_LOCKED;
set_fs_pwd(current->fs, &root);
set_fs_root(current->fs, &root);
diff --git a/fs/pnode.c b/fs/pnode.c
index aae331a5d03b..260ac8f898a4 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -242,6 +242,7 @@ static int propagate_one(struct mount *m)
child = copy_tree(last_source, last_source->mnt.mnt_root, type);
if (IS_ERR(child))
return PTR_ERR(child);
+ child->mnt.mnt_flags &= ~MNT_LOCKED;
mnt_set_mountpoint(m, mp, child);
last_dest = m;
last_source = child;
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 590aeda5af12..3f3d7aeb0712 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2464,6 +2464,57 @@ static const struct file_operations proc_projid_map_operations = {
.llseek = seq_lseek,
.release = proc_id_map_release,
};
+
+static int proc_setgroups_open(struct inode *inode, struct file *file)
+{
+ struct user_namespace *ns = NULL;
+ struct task_struct *task;
+ int ret;
+
+ ret = -ESRCH;
+ task = get_proc_task(inode);
+ if (task) {
+ rcu_read_lock();
+ ns = get_user_ns(task_cred_xxx(task, user_ns));
+ rcu_read_unlock();
+ put_task_struct(task);
+ }
+ if (!ns)
+ goto err;
+
+ if (file->f_mode & FMODE_WRITE) {
+ ret = -EACCES;
+ if (!ns_capable(ns, CAP_SYS_ADMIN))
+ goto err_put_ns;
+ }
+
+ ret = single_open(file, &proc_setgroups_show, ns);
+ if (ret)
+ goto err_put_ns;
+
+ return 0;
+err_put_ns:
+ put_user_ns(ns);
+err:
+ return ret;
+}
+
+static int proc_setgroups_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *seq = file->private_data;
+ struct user_namespace *ns = seq->private;
+ int ret = single_release(inode, file);
+ put_user_ns(ns);
+ return ret;
+}
+
+static const struct file_operations proc_setgroups_operations = {
+ .open = proc_setgroups_open,
+ .write = proc_setgroups_write,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = proc_setgroups_release,
+};
#endif /* CONFIG_USER_NS */
static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
@@ -2572,6 +2623,7 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("uid_map", S_IRUGO|S_IWUSR, proc_uid_map_operations),
REG("gid_map", S_IRUGO|S_IWUSR, proc_gid_map_operations),
REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
+ REG("setgroups", S_IRUGO|S_IWUSR, proc_setgroups_operations),
#endif
#ifdef CONFIG_CHECKPOINT_RESTORE
REG("timers", S_IRUGO, proc_timers_operations),
@@ -2916,6 +2968,7 @@ static const struct pid_entry tid_base_stuff[] = {
REG("uid_map", S_IRUGO|S_IWUSR, proc_uid_map_operations),
REG("gid_map", S_IRUGO|S_IWUSR, proc_gid_map_operations),
REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
+ REG("setgroups", S_IRUGO|S_IWUSR, proc_setgroups_operations),
#endif
};