Re: [PATCH v23 03/22] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags

Jeff Layton
2016-07-05T11:07:54Z

On Thu, 2016-06-30 at 15:46 +0200, Andreas Gruenbacher wrote:
> Normally, deleting a file requires MAY_WRITE access to the parent
> directory.  With richacls, a file may be deleted with MAY_DELETE_CHILD access
> to the parent directory or with MAY_DELETE_SELF access to the file.
>
> To support that, pass the MAY_DELETE_CHILD mask flag to inode_permission()
> when checking for delete access inside a directory, and MAY_DELETE_SELF
> when checking for delete access to a file itelf.
>

Minor misspelling in changelog above. It should be "itself".

> The MAY_DELETE_SELF permission overrides the sticky directory check.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
> Reviewed-by: J. Bruce Fields <bfields@redhat.com>
> Reviewed-by: Steve French <steve.french@primarydata.com>
> ---
>  fs/namei.c         | 20 ++++++++++++--------
>  include/linux/fs.h |  2 ++
>  2 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index dc91858..663933e 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -454,9 +454,9 @@ static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
>   * this, letting us set arbitrary permissions for filesystem access without
>   * changing the "normal" UIDs which are used for other things.
>   *
> - * MAY_WRITE must be set in @mask whenever MAY_APPEND, MAY_CREATE_FILE, or
> - * MAY_CREATE_DIR are set.  That way, file systems that don't support these
> - * permissions will check for MAY_WRITE instead.
> + * MAY_WRITE must be set in @mask whenever MAY_APPEND, MAY_CREATE_FILE,
> + * MAY_CREATE_DIR, or MAY_DELETE_CHILD are set.  That way, file systems that
> + * don't support these permissions will check for MAY_WRITE instead.
>   */
>  int inode_permission(struct inode *inode, int mask)
>  {
> @@ -2778,14 +2778,18 @@ static int may_delete_or_replace(struct inode *dir, struct dentry *victim,
>   BUG_ON(victim->d_parent->d_inode != dir);
>   audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
>
> - error = inode_permission(dir, mask);
> + error = inode_permission(dir, mask | MAY_WRITE | MAY_DELETE_CHILD);
> + if (!error && check_sticky(dir, inode))
> + error = -EPERM;
> + if (error && IS_RICHACL(inode) &&
> +     inode_permission(inode, MAY_DELETE_SELF) == 0 &&
> +     inode_permission(dir, mask) == 0)
> + error = 0;
>   if (error)
>   return error;
>   if (IS_APPEND(dir))
>   return -EPERM;
> -
> - if (check_sticky(dir, inode) || IS_APPEND(inode) ||
> -     IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
> + if (IS_APPEND(inode) || IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
>   return -EPERM;
>   if (isdir) {
>   if (!d_is_dir(victim))
> @@ -2803,7 +2807,7 @@ static int may_delete_or_replace(struct inode *dir, struct dentry *victim,
>
>  static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
>  {
> - return may_delete_or_replace(dir, victim, isdir, MAY_WRITE | MAY_EXEC);
> + return may_delete_or_replace(dir, victim, isdir, MAY_EXEC);
>  }
>
>  static int may_replace(struct inode *dir, struct dentry *victim, bool isdir)
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index dd614ad..86bfa10 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -86,6 +86,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
>  #define MAY_NOT_BLOCK 0x00000080
>  #define MAY_CREATE_FILE 0x00000100
>  #define MAY_CREATE_DIR 0x00000200
> +#define MAY_DELETE_CHILD 0x00000400
> +#define MAY_DELETE_SELF 0x00000800
>
>  /*
>   * flags in file.f_mode.  Note that FMODE_READ and FMODE_WRITE must correspond

Reviewed-by: Jeff Layton <jlayton@redhat.com>