In message <1256152779-10054-23-git-send-email-vaurora@xxxxxxxxxx>, Valerie Aurora writes:
> From: Jan Blunck <jblunck@xxxxxxx>
>
> Add some additional checks when mounting something into an union.
The text "add some additional checks" seems to imply "code I forgot to add
earlier". If this patch is better merged with some other one, then do so;
otherwise, the subject line and patch header need to give this patch more
credit than this: better explain what the checks are more precisely.
> Signed-off-by: Jan Blunck <jblunck@xxxxxxx>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
> Signed-off-by: Valerie Aurora <vaurora@xxxxxxxxxx>
> ---
> 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;
> }
I'd avoid using 'exit' as a label and goto name; use "out_err" or some other
out_XXX label. 'exit' is almost a reserved word in C. :-)
> @@ -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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Erez.
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