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Subject[PATCH 22/41] union-mount: Some checks during namespace changes
Date
From: Jan Blunck <jblunck@suse.de>

Add some additional checks when mounting something into an union.

Signed-off-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Valerie Aurora <vaurora@redhat.com>
---
fs/namespace.c | 34 ++++++++++++++++++++++++++++++++++
1 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 81b3188..dc01385 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -29,6 +29,7 @@
#include <linux/log2.h>
#include <linux/idr.h>
#include <linux/fs_struct.h>
+#include <linux/union.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include "pnode.h"
@@ -1427,6 +1428,10 @@ static int do_change_type(struct path *path, int flag)
if (path->dentry != path->mnt->mnt_root)
return -EINVAL;

+ /* Don't change the type of union mounts */
+ if (IS_MNT_UNION(path->mnt))
+ return -EINVAL;
+
down_write(&namespace_sem);
if (type == MS_SHARED) {
err = invent_group_ids(mnt, recurse);
@@ -1478,6 +1483,18 @@ static int do_loopback(struct path *path, char *old_name, int recurse,
if (!mnt)
goto out;

+ /*
+ * Unions couldn't be writable if the filesystem doesn't know about
+ * whiteouts
+ */
+ err = -ENOTSUPP;
+ if ((mnt_flags & MNT_UNION) &&
+ !(mnt->mnt_sb->s_flags & (MS_WHITEOUT|MS_RDONLY)))
+ goto out;
+
+ if (mnt_flags & MNT_UNION)
+ mnt->mnt_flags |= MNT_UNION;
+
err = graft_tree(mnt, path);
if (err) {
LIST_HEAD(umount_list);
@@ -1571,6 +1588,13 @@ static int do_move_mount(struct path *path, char *old_name)
if (err)
return err;

+ /* moving to or from a union mount is not supported */
+ err = -EINVAL;
+ if (IS_MNT_UNION(path->mnt))
+ goto exit;
+ if (IS_MNT_UNION(old_path.mnt))
+ goto exit;
+
down_write(&namespace_sem);
while (d_mountpoint(path->dentry) &&
follow_down(path))
@@ -1628,6 +1652,7 @@ out:
up_write(&namespace_sem);
if (!err)
path_put(&parent_path);
+exit:
path_put(&old_path);
return err;
}
@@ -1685,6 +1710,15 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path,
if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
goto unlock;

+ /*
+ * Unions couldn't be writable if the filesystem doesn't know about
+ * whiteouts
+ */
+ err = -ENOTSUPP;
+ if ((mnt_flags & MNT_UNION) &&
+ !(newmnt->mnt_sb->s_flags & (MS_WHITEOUT|MS_RDONLY)))
+ goto unlock;
+
newmnt->mnt_flags = mnt_flags;
if ((err = graft_tree(newmnt, path)))
goto unlock;
--
1.6.3.3


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