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

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Date:	Thu, 01 May 2014 20:46:41 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Dave Chinner <david@...morbit.com>,
	Jeff Layton <jlayton@...chiereds.net>
Cc:	agruen@...nel.org, bfields@...ldses.org, akpm@...ux-foundation.org,
	viro@...iv.linux.org.uk, dhowells@...hat.com,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -V1 05/22] vfs: Add new file and directory create permission flags

Dave Chinner <david@...morbit.com> writes:

> 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@...ux.vnet.ibm.com> wrote:
>> 
>> > From: Andreas Gruenbacher <agruen@...nel.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@...nel.org>
>> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.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()....

Will do that.

Thanks
-aneesh

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