linux-kernel - Re: [PATCH 04/13] Apparmor: Use simple_start_creating() / simple_done

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Message-id: <177033726944.16766.14495020155654514261@noble.neil.brown.name>
Date: Fri, 06 Feb 2026 11:21:09 +1100
From: NeilBrown <neilb@...mail.net>
To: "Jeff Layton" <jlayton@...nel.org>
Cc: "Christian Brauner" <brauner@...nel.org>,
 "Alexander Viro" <viro@...iv.linux.org.uk>,
 "David Howells" <dhowells@...hat.com>, "Jan Kara" <jack@...e.cz>,
 "Chuck Lever" <chuck.lever@...cle.com>, "Miklos Szeredi" <miklos@...redi.hu>,
 "Amir Goldstein" <amir73il@...il.com>,
 "John Johansen" <john.johansen@...onical.com>,
 "Paul Moore" <paul@...l-moore.com>, "James Morris" <jmorris@...ei.org>,
 "Serge E. Hallyn" <serge@...lyn.com>,
 "Stephen Smalley" <stephen.smalley.work@...il.com>,
 linux-kernel@...r.kernel.org, netfs@...ts.linux.dev,
 linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
 linux-unionfs@...r.kernel.org, apparmor@...ts.ubuntu.com,
 linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH 04/13] Apparmor: Use simple_start_creating() /
 simple_done_creating()

On Thu, 05 Feb 2026, Jeff Layton wrote:
> On Wed, 2026-02-04 at 15:57 +1100, NeilBrown wrote:
> > From: NeilBrown <neil@...wn.name>
> > 
> > Instead of explicitly locking the parent and performing a look up in
> > apparmor, use simple_start_creating(), and then simple_done_creating()
> > to unlock and drop the dentry.
> > 
> > This removes the need to check for an existing entry (as
> > simple_start_creating() acts like an exclusive create and can return
> > -EEXIST), simplifies error paths, and keeps dir locking code
> > centralised.
> > 
> > Signed-off-by: NeilBrown <neil@...wn.name>
> > ---
> >  security/apparmor/apparmorfs.c | 38 ++++++++--------------------------
> >  1 file changed, 9 insertions(+), 29 deletions(-)
> > 
> > diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
> > index 907bd2667e28..7f78c36e6e50 100644
> > --- a/security/apparmor/apparmorfs.c
> > +++ b/security/apparmor/apparmorfs.c
> > @@ -282,32 +282,19 @@ static struct dentry *aafs_create(const char *name, umode_t mode,
> >  
> >  	dir = d_inode(parent);
> >  
> > -	inode_lock(dir);
> > -	dentry = lookup_noperm(&QSTR(name), parent);
> > +	dentry = simple_start_creating(parent, name);
> >  	if (IS_ERR(dentry)) {
> >  		error = PTR_ERR(dentry);
> > -		goto fail_lock;
> > -	}
> > -
> > -	if (d_really_is_positive(dentry)) {
> > -		error = -EEXIST;
> > -		goto fail_dentry;
> > +		goto fail;
> >  	}
> >  
> >  	error = __aafs_setup_d_inode(dir, dentry, mode, data, link, fops, iops);
> > +	simple_done_creating(dentry);
> >  	if (error)
> > -		goto fail_dentry;
> > -	inode_unlock(dir);
> > -
> > -	return dentry;
> > -
> > -fail_dentry:
> > -	dput(dentry);
> > -
> > -fail_lock:
> > -	inode_unlock(dir);
> > +		goto fail;
> > +	return 0;
> 
> As KTR points out, this should be "return NULL;"

Actually it should be "return dentry;" which is what the original code
did.
I've no idea how it became 0...
Callers of aafs_create() will silently treat NULL as failure.

> 
> > +fail:
> >  	simple_release_fs(&aafs_mnt, &aafs_count);
> > -
> >  	return ERR_PTR(error);
> >  }
> >  
> > @@ -2572,8 +2559,7 @@ static int aa_mk_null_file(struct dentry *parent)
> >  	if (error)
> >  		return error;
> >  
> > -	inode_lock(d_inode(parent));
> > -	dentry = lookup_noperm(&QSTR(NULL_FILE_NAME), parent);
> > +	dentry = simple_start_creating(parent, NULL_FILE_NAME);
> >  	if (IS_ERR(dentry)) {
> >  		error = PTR_ERR(dentry);
> >  		goto out;
> > @@ -2581,7 +2567,7 @@ static int aa_mk_null_file(struct dentry *parent)
> >  	inode = new_inode(parent->d_inode->i_sb);
> >  	if (!inode) {
> >  		error = -ENOMEM;
> > -		goto out1;
> > +		goto out;
> >  	}
> >  
> >  	inode->i_ino = get_next_ino();
> > @@ -2593,18 +2579,12 @@ static int aa_mk_null_file(struct dentry *parent)
> >  	aa_null.dentry = dget(dentry);
> >  	aa_null.mnt = mntget(mount);
> >  
> > -	error = 0;
> > -
> > -out1:
> > -	dput(dentry);
> >  out:
> > -	inode_unlock(d_inode(parent));
> > +	simple_done_creating(dentry);
> >  	simple_release_fs(&mount, &count);
> >  	return error;
> >  }
> >  
> > -
> > -
> >  static const char *policy_get_link(struct dentry *dentry,
> >  				   struct inode *inode,
> >  				   struct delayed_call *done)
> 
> Assuming you fix the minor problem above.
> 
> Reviewed-by: Jeff Layton <jlayton@...nel.org>
> 

Thanks,
NeilBrown