On Tue, Aug 04, 2015 at 01:53:01PM +0200, Andreas Gruenbacher wrote:
> Normally, deleting a file requires write and execute access to the parent
> directory. With Richacls, a process with MAY_DELETE_SELF access to a file
> may delete the file even without write access to the parent directory.
>
> 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.
>
> The MAY_DELETE_SELF permission does not override the sticky directory
> check. It probably should.
I guess it would basically just let the file owner delegate permission
to delete your file to a non-owner? Makes sense to me to allow that.
--b.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> ---
> fs/namei.c | 15 +++++++++++----
> include/linux/fs.h | 2 ++
> 2 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 3504d36..2ac759c 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -454,7 +454,7 @@ static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
> * changing the "normal" UIDs which are used for other things.
> *
> * When checking for MAY_APPEND, MAY_CREATE_FILE, MAY_CREATE_DIR,
> - * MAY_WRITE must also be set in @mask.
> + * MAY_DELETE_CHILD, MAY_DELETE_SELF, MAY_WRITE must also be set in @mask.
> */
> int inode_permission(struct inode *inode, int mask)
> {
> @@ -2527,7 +2527,7 @@ static int may_delete(struct inode *dir, struct dentry *victim,
> bool isdir, bool replace)
> {
> struct inode *inode = d_backing_inode(victim);
> - int error, mask = MAY_WRITE | MAY_EXEC;
> + int error, mask = MAY_EXEC;
>
> if (d_is_negative(victim))
> return -ENOENT;
> @@ -2537,8 +2537,15 @@ static int may_delete(struct inode *dir, struct dentry *victim,
> audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
>
> if (replace)
> - mask |= isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE;
> - error = inode_permission(dir, mask);
> + mask |= MAY_WRITE | (isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE);
> + error = inode_permission(dir, mask | MAY_WRITE | MAY_DELETE_CHILD);
> + if (error && IS_RICHACL(inode)) {
> + /* Deleting is also permitted with MAY_EXEC on the directory
> + * and MAY_DELETE_SELF on the inode. */
> + if (!inode_permission(inode, MAY_DELETE_SELF) &&
> + !inode_permission(dir, mask))
> + error = 0;
> + }
> if (error)
> return error;
> if (IS_APPEND(dir))
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9c44f27..abf5b0e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -83,6 +83,8 @@ typedef void (dax_iodone_t)(struct buffer_head *bh_map, int uptodate);
> #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
> --
> 2.5.0
>
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