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-rw-r--r--fs/namespace.c121
-rw-r--r--fs/open.c2
-rw-r--r--fs/pnode.h5
-rw-r--r--fs/proc/root.c6
-rw-r--r--fs/sysfs/mount.c11
5 files changed, 114 insertions, 31 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index ad8ea9bc2518..ef69fa5d2e5b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -831,6 +831,10 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
+ /* Don't allow unprivileged users to reveal what is under a mount */
+ if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
+ mnt->mnt.mnt_flags |= MNT_LOCKED;
+
atomic_inc(&sb->s_active);
mnt->mnt.mnt_sb = sb;
mnt->mnt.mnt_root = dget(root);
@@ -1327,6 +1331,8 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
goto dput_and_out;
if (!check_mnt(mnt))
goto dput_and_out;
+ if (mnt->mnt.mnt_flags & MNT_LOCKED)
+ goto dput_and_out;
retval = do_umount(mnt, flags);
dput_and_out:
@@ -1349,14 +1355,11 @@ SYSCALL_DEFINE1(oldumount, char __user *, name)
#endif
-static bool mnt_ns_loop(struct path *path)
+static bool is_mnt_ns_file(struct dentry *dentry)
{
- /* Could bind mounting the mount namespace inode cause a
- * mount namespace loop?
- */
- struct inode *inode = path->dentry->d_inode;
+ /* Is this a proxy for a mount namespace? */
+ struct inode *inode = dentry->d_inode;
struct proc_ns *ei;
- struct mnt_namespace *mnt_ns;
if (!proc_ns_inode(inode))
return false;
@@ -1365,7 +1368,19 @@ static bool mnt_ns_loop(struct path *path)
if (ei->ns_ops != &mntns_operations)
return false;
- mnt_ns = ei->ns;
+ return true;
+}
+
+static bool mnt_ns_loop(struct dentry *dentry)
+{
+ /* Could bind mounting the mount namespace inode cause a
+ * mount namespace loop?
+ */
+ struct mnt_namespace *mnt_ns;
+ if (!is_mnt_ns_file(dentry))
+ return false;
+
+ mnt_ns = get_proc_ns(dentry->d_inode)->ns;
return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
}
@@ -1374,13 +1389,17 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
{
struct mount *res, *p, *q, *r, *parent;
- if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
+ if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
+ return ERR_PTR(-EINVAL);
+
+ if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
return ERR_PTR(-EINVAL);
res = q = clone_mnt(mnt, dentry, flag);
if (IS_ERR(q))
return q;
+ q->mnt.mnt_flags &= ~MNT_LOCKED;
q->mnt_mountpoint = mnt->mnt_mountpoint;
p = mnt;
@@ -1390,7 +1409,13 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
continue;
for (s = r; s; s = next_mnt(s, r)) {
- if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
+ if (!(flag & CL_COPY_UNBINDABLE) &&
+ IS_MNT_UNBINDABLE(s)) {
+ s = skip_mnt_tree(s);
+ continue;
+ }
+ if (!(flag & CL_COPY_MNT_NS_FILE) &&
+ is_mnt_ns_file(s->mnt.mnt_root)) {
s = skip_mnt_tree(s);
continue;
}
@@ -1696,6 +1721,19 @@ static int do_change_type(struct path *path, int flag)
return err;
}
+static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
+{
+ struct mount *child;
+ list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
+ if (!is_subdir(child->mnt_mountpoint, dentry))
+ continue;
+
+ if (child->mnt.mnt_flags & MNT_LOCKED)
+ return true;
+ }
+ return false;
+}
+
/*
* do loopback mount.
*/
@@ -1713,7 +1751,7 @@ static int do_loopback(struct path *path, const char *old_name,
return err;
err = -EINVAL;
- if (mnt_ns_loop(&old_path))
+ if (mnt_ns_loop(old_path.dentry))
goto out;
mp = lock_mount(path);
@@ -1731,8 +1769,11 @@ static int do_loopback(struct path *path, const char *old_name,
if (!check_mnt(parent) || !check_mnt(old))
goto out2;
+ if (!recurse && has_locked_children(old, old_path.dentry))
+ goto out2;
+
if (recurse)
- mnt = copy_tree(old, old_path.dentry, 0);
+ mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
else
mnt = clone_mnt(old, old_path.dentry, 0);
@@ -1741,6 +1782,8 @@ static int do_loopback(struct path *path, const char *old_name,
goto out2;
}
+ mnt->mnt.mnt_flags &= ~MNT_LOCKED;
+
err = graft_tree(mnt, parent, mp);
if (err) {
br_write_lock(&vfsmount_lock);
@@ -1853,6 +1896,9 @@ static int do_move_mount(struct path *path, const char *old_name)
if (!check_mnt(p) || !check_mnt(old))
goto out1;
+ if (old->mnt.mnt_flags & MNT_LOCKED)
+ goto out1;
+
err = -EINVAL;
if (old_path.dentry != old_path.mnt->mnt_root)
goto out1;
@@ -2389,7 +2435,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
namespace_lock();
/* First pass: copy the tree topology */
- copy_flags = CL_COPY_ALL | CL_EXPIRE;
+ copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
if (user_ns != mnt_ns->user_ns)
copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
new = copy_tree(old, old->mnt.mnt_root, copy_flags);
@@ -2424,6 +2470,10 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
}
p = next_mnt(p, old);
q = next_mnt(q, new);
+ if (!q)
+ break;
+ while (p->mnt.mnt_root != q->mnt.mnt_root)
+ p = next_mnt(p, old);
}
namespace_unlock();
@@ -2630,6 +2680,8 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
goto out4;
if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
goto out4;
+ if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
+ goto out4;
error = -ENOENT;
if (d_unlinked(new.dentry))
goto out4;
@@ -2653,6 +2705,10 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
br_write_lock(&vfsmount_lock);
detach_mnt(new_mnt, &parent_path);
detach_mnt(root_mnt, &root_parent);
+ if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
+ new_mnt->mnt.mnt_flags |= MNT_LOCKED;
+ root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
+ }
/* mount old root on put_old */
attach_mnt(root_mnt, old_mnt, old_mp);
/* mount new_root on / */
@@ -2811,25 +2867,38 @@ bool current_chrooted(void)
return chrooted;
}
-void update_mnt_policy(struct user_namespace *userns)
+bool fs_fully_visible(struct file_system_type *type)
{
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
struct mount *mnt;
+ bool visible = false;
- down_read(&namespace_sem);
+ if (unlikely(!ns))
+ return false;
+
+ namespace_lock();
list_for_each_entry(mnt, &ns->list, mnt_list) {
- switch (mnt->mnt.mnt_sb->s_magic) {
- case SYSFS_MAGIC:
- userns->may_mount_sysfs = true;
- break;
- case PROC_SUPER_MAGIC:
- userns->may_mount_proc = true;
- break;
+ struct mount *child;
+ if (mnt->mnt.mnt_sb->s_type != type)
+ continue;
+
+ /* This mount is not fully visible if there are any child mounts
+ * that cover anything except for empty directories.
+ */
+ list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
+ struct inode *inode = child->mnt_mountpoint->d_inode;
+ if (!S_ISDIR(inode->i_mode))
+ goto next;
+ if (inode->i_nlink != 2)
+ goto next;
}
- if (userns->may_mount_sysfs && userns->may_mount_proc)
- break;
+ visible = true;
+ goto found;
+ next: ;
}
- up_read(&namespace_sem);
+found:
+ namespace_unlock();
+ return visible;
}
static void *mntns_get(struct task_struct *task)
@@ -2860,8 +2929,8 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns)
struct path root;
if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
- !nsown_capable(CAP_SYS_CHROOT) ||
- !nsown_capable(CAP_SYS_ADMIN))
+ !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
+ !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
return -EPERM;
if (fs->users != 1)
diff --git a/fs/open.c b/fs/open.c
index 8070825b285b..2a731b0d08bc 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -443,7 +443,7 @@ retry:
goto dput_and_out;
error = -EPERM;
- if (!nsown_capable(CAP_SYS_CHROOT))
+ if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
goto dput_and_out;
error = security_path_chroot(&path);
if (error)
diff --git a/fs/pnode.h b/fs/pnode.h
index b091445c1c4a..59e7eda1851e 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -19,11 +19,14 @@
#define CL_EXPIRE 0x01
#define CL_SLAVE 0x02
-#define CL_COPY_ALL 0x04
+#define CL_COPY_UNBINDABLE 0x04
#define CL_MAKE_SHARED 0x08
#define CL_PRIVATE 0x10
#define CL_SHARED_TO_SLAVE 0x20
#define CL_UNPRIVILEGED 0x40
+#define CL_COPY_MNT_NS_FILE 0x80
+
+#define CL_COPY_ALL (CL_COPY_UNBINDABLE | CL_COPY_MNT_NS_FILE)
static inline void set_mnt_shared(struct mount *mnt)
{
diff --git a/fs/proc/root.c b/fs/proc/root.c
index e0a790da726d..87dbcbef7fe4 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -110,7 +110,11 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
ns = task_active_pid_ns(current);
options = data;
- if (!current_user_ns()->may_mount_proc)
+ if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
+ return ERR_PTR(-EPERM);
+
+ /* Does the mounter have privilege over the pid namespace? */
+ if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
}
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index fd7ce7a39f91..834ec2cdb7a3 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -112,8 +112,15 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
struct super_block *sb;
int error;
- if (!(flags & MS_KERNMOUNT) && !current_user_ns()->may_mount_sysfs)
- return ERR_PTR(-EPERM);
+ if (!(flags & MS_KERNMOUNT)) {
+ if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
+ return ERR_PTR(-EPERM);
+
+ for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
+ if (!kobj_ns_current_may_mount(type))
+ return ERR_PTR(-EPERM);
+ }
+ }
info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info)
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.