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-rw-r--r--fs/namespace.c39
1 files changed, 33 insertions, 6 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index e99f1f4e00cd..c7cb8a526c05 100644
--- 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: ;