Merge tag 'staging-4.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh...

[platform/kernel/linux-starfive.git] / fs / namespace.c

diff --git a/fs/namespace.c b/fs/namespace.c
index e99f1f4..2b8aa15 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1361,6 +1361,36 @@ enum umount_tree_flags {
        UMOUNT_PROPAGATE = 2,
        UMOUNT_CONNECTED = 4,
 };
+
+static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
+{
+       /* Leaving mounts connected is only valid for lazy umounts */
+       if (how & UMOUNT_SYNC)
+               return true;
+
+       /* A mount without a parent has nothing to be connected to */
+       if (!mnt_has_parent(mnt))
+               return true;
+
+       /* Because the reference counting rules change when mounts are
+        * unmounted and connected, umounted mounts may not be
+        * connected to mounted mounts.
+        */
+       if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
+               return true;
+
+       /* Has it been requested that the mount remain connected? */
+       if (how & UMOUNT_CONNECTED)
+               return false;
+
+       /* Is the mount locked such that it needs to remain connected? */
+       if (IS_MNT_LOCKED(mnt))
+               return false;
+
+       /* By default disconnect the mount */
+       return true;
+}
+
 /*
  * mount_lock must be held
  * namespace_sem must be held for write
@@ -1398,10 +1428,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
                if (how & UMOUNT_SYNC)
                        p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
 
-               disconnect = !(((how & UMOUNT_CONNECTED) &&
-                               mnt_has_parent(p) &&
-                               (p->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) ||
-                              IS_MNT_LOCKED_AND_LAZY(p));
+               disconnect = disconnect_mount(p, how);
 
                pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt,
                                 disconnect ? &unmounted : NULL);
@@ -1538,11 +1565,8 @@ void __detach_mounts(struct dentry *dentry)
        while (!hlist_empty(&mp->m_list)) {
                mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
                if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
-                       struct mount *p, *tmp;
-                       list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts,  mnt_child) {
-                               hlist_add_head(&p->mnt_umount.s_list, &unmounted);
-                               umount_mnt(p);
-                       }
+                       hlist_add_head(&mnt->mnt_umount.s_list, &unmounted);
+                       umount_mnt(mnt);
                }
                else umount_tree(mnt, UMOUNT_CONNECTED);
        }
@@ -2343,6 +2367,8 @@ unlock:
        return err;
 }
 
+static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags);
+
 /*
  * create a new mount for userspace and request it to be added into the
  * namespace's tree
@@ -2374,6 +2400,10 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
                        flags |= MS_NODEV;
                        mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
                }
+               if (type->fs_flags & FS_USERNS_VISIBLE) {
+                       if (!fs_fully_visible(type, &mnt_flags))
+                               return -EPERM;
+               }
        }
 
        mnt = vfs_kern_mount(type, flags, name, data);
@@ -3175,9 +3205,10 @@ bool current_chrooted(void)
        return chrooted;
 }
 
-bool fs_fully_visible(struct file_system_type *type)
+static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
 {
        struct mnt_namespace *ns = current->nsproxy->mnt_ns;
+       int new_flags = *new_mnt_flags;
        struct mount *mnt;
        bool visible = false;
 
@@ -3196,16 +3227,36 @@ bool fs_fully_visible(struct file_system_type *type)
                if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
                        continue;
 
-               /* This mount is not fully visible if there are any child mounts
-                * that cover anything except for empty directories.
+               /* Verify the mount flags are equal to or more permissive
+                * than the proposed new mount.
+                */
+               if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
+                   !(new_flags & MNT_READONLY))
+                       continue;
+               if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
+                   !(new_flags & MNT_NODEV))
+                       continue;
+               if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) &&
+                   ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
+                       continue;
+
+               /* This mount is not fully visible if there are any
+                * locked 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)
+                       /* Only worry about locked mounts */
+                       if (!(mnt->mnt.mnt_flags & MNT_LOCKED))
+                               continue;
+                       /* Is the directory permanetly empty? */
+                       if (!is_empty_dir_inode(inode))
                                goto next;
                }
+               /* Preserve the locked attributes */
+               *new_mnt_flags |= mnt->mnt.mnt_flags & (MNT_LOCK_READONLY | \
+                                                       MNT_LOCK_NODEV    | \
+                                                       MNT_LOCK_ATIME);
                visible = true;
                goto found;
        next:   ;