1 files changed, 21 insertions, 3 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 8e7edaf60fe1..63b9806235e6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2332,7 +2332,7 @@ unlock:
         return err;
 }
 
-static bool fs_fully_visible(struct file_system_type *fs_type);
+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
@@ -2366,7 +2366,7 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
                         mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
                 }
                 if (type->fs_flags & FS_USERNS_VISIBLE) {
-                        if (!fs_fully_visible(type))
+                        if (!fs_fully_visible(type, &mnt_flags))
                                 return -EPERM;
                 }
         }
@@ -3170,9 +3170,10 @@ bool current_chrooted(void)
         return chrooted;
 }
 
-static 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;
 
@@ -3191,6 +3192,19 @@ static bool fs_fully_visible(struct file_system_type *type)
                 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
                         continue;
 
+                /* 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 child mounts
                  * that cover anything except for empty directories.
                  */
@@ -3201,6 +3215,10 @@ static bool fs_fully_visible(struct file_system_type *type)
                         if (inode->i_nlink > 2)
                                 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:   ;