Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm...

[linux-drm-fsl-dcu.git] / fs / namespace.c

diff --git a/fs/namespace.c b/fs/namespace.c
index e99f1f4e00cd93a0d2217bf736e8bf896780ebe4..c7cb8a526c05fbaa5ba18934cd04eda1eb2a6e60 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2343,6 +2343,8 @@ 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 +2376,10 @@ 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 +3181,10 @@ 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 +3203,36 @@ 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:   ;