Re: [PATCH -V1 05/22] vfs: Add new file and directory create permission flags

Dave Chinner
2014-04-29T00:06:00Z

On Mon, Apr 28, 2014 at 07:23:01AM -0400, Jeff Layton wrote:
> On Sun, 27 Apr 2014 21:44:36 +0530
> "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
>
> > From: Andreas Gruenbacher <agruen@kernel.org>
> >
> > Some permission models distinguish between the permission to create a
> > non-directory and a directory. Pass this information down to
> > inode_permission() as mask flags
> >
> > Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> > ---
> > fs/namei.c | 21 ++++++++++++---------
> > include/linux/fs.h | 2 ++
> > 2 files changed, 14 insertions(+), 9 deletions(-)
> >
> > diff --git a/fs/namei.c b/fs/namei.c
> > index 7d93d195f0e5..028bc8bcf77c 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -445,7 +445,8 @@ 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.
> > *
> > - * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
> > + * When checking for MAY_APPEND, MAY_CREATE_FILE, MAY_CREATE_DIR,
> > + * MAY_WRITE must also be set in @mask.
> > */
> > int inode_permission(struct inode *inode, int mask)
> > {
> > @@ -2444,14 +2445,16 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
> > * 3. We should have write and exec permissions on dir
> > * 4. We can't do it if dir is immutable (done in permission())
> > */
> > -static inline int may_create(struct inode *dir, struct dentry *child)
> > +static inline int may_create(struct inode *dir, struct dentry *child, bool isdir)
> > {
> > + int mask = isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE;
> > +
> > audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
> > if (child->d_inode)
> > return -EEXIST;
> > if (IS_DEADDIR(dir))
> > return -ENOENT;
> > - return inode_permission(dir, MAY_WRITE | MAY_EXEC);
> > + return inode_permission(dir, MAY_WRITE | MAY_EXEC | mask);
> > }
> >
> > /*
> > @@ -2501,7 +2504,7 @@ EXPORT_SYMBOL(unlock_rename);
> > int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
> > bool want_excl)
> > {
> > - int error = may_create(dir, dentry);
> > + int error = may_create(dir, dentry, 0);
>
> nit: since the third argument here is a bool, this should be "false"
> and not "0". Ditto for all of the other calls of may_create.

IMO, the third argument should be MAY_CREATE_FILE or MAY_CREATE_DIR,
which is what the boolean evaluates to in may_create()....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com