linux-kernel - Re: [PATCH v3 5/5] ramfs: Initialize security of in-memory inodes

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Date: Fri, 26 Jan 2024 08:53:27 +0100
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: casey@...aufler-ca.com, paul@...l-moore.com, jmorris@...ei.org, 
 serge@...lyn.com, linux-kernel@...r.kernel.org, 
 linux-security-module@...r.kernel.org, Roberto Sassu
 <roberto.sassu@...wei.com>,  Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH v3 5/5] ramfs: Initialize security of in-memory inodes

On Thu, 2024-01-25 at 17:08 -0800, Andrew Morton wrote:
> On Thu, 16 Nov 2023 10:01:25 +0100 Roberto Sassu <roberto.sassu@...weicloud.com> wrote:
> 
> > From: Roberto Sassu <roberto.sassu@...wei.com>
> > 
> > Add a call security_inode_init_security() after ramfs_get_inode(), to let
> > LSMs initialize the inode security field. Skip ramfs_fill_super(), as the
> > initialization is done through the sb_set_mnt_opts hook.
> > 
> > Calling security_inode_init_security() call inside ramfs_get_inode() is
> > not possible since, for CONFIG_SHMEM=n, tmpfs also calls the former after
> > the latter.
> > 
> > Pass NULL as initxattrs() callback to security_inode_init_security(), since
> > the purpose of the call is only to initialize the in-memory inodes.
> > 
> 
> fwiw,
> 
> Acked-by: Andrew Morton <akpm@...ux-foundation.org>
> 
> Please include this in the relevant security tree.

Thanks a lot!

Roberto

> > diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
> > index 4ac05a9e25bc..8006faaaf0ec 100644
> > --- a/fs/ramfs/inode.c
> > +++ b/fs/ramfs/inode.c
> > @@ -102,11 +102,20 @@ ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
> >  	int error = -ENOSPC;
> >  
> >  	if (inode) {
> > +		error = security_inode_init_security(inode, dir,
> > +						     &dentry->d_name, NULL,
> > +						     NULL);
> > +		if (error) {
> > +			iput(inode);
> > +			goto out;
> > +		}
> > +
> >  		d_instantiate(dentry, inode);
> >  		dget(dentry);	/* Extra count - pin the dentry in core */
> >  		error = 0;
> >  		inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
> >  	}
> > +out:
> >  	return error;
> >  }
> >  
> > @@ -134,6 +143,15 @@ static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
> >  	inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
> >  	if (inode) {
> >  		int l = strlen(symname)+1;
> > +
> > +		error = security_inode_init_security(inode, dir,
> > +						     &dentry->d_name, NULL,
> > +						     NULL);
> > +		if (error) {
> > +			iput(inode);
> > +			goto out;
> > +		}
> > +
> >  		error = page_symlink(inode, symname, l);
> >  		if (!error) {
> >  			d_instantiate(dentry, inode);
> > @@ -143,6 +161,7 @@ static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
> >  		} else
> >  			iput(inode);
> >  	}
> > +out:
> >  	return error;
> >  }
> >  
> > @@ -150,12 +169,23 @@ static int ramfs_tmpfile(struct mnt_idmap *idmap,
> >  			 struct inode *dir, struct file *file, umode_t mode)
> >  {
> >  	struct inode *inode;
> > +	int error;
> >  
> >  	inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
> >  	if (!inode)
> >  		return -ENOSPC;
> > +
> > +	error = security_inode_init_security(inode, dir,
> > +					     &file_dentry(file)->d_name, NULL,
> > +					     NULL);
> > +	if (error) {
> > +		iput(inode);
> > +		goto out;
> > +	}
> > +
> >  	d_tmpfile(file, inode);
> > -	return finish_open_simple(file, 0);
> > +out:
> > +	return finish_open_simple(file, error);
> >  }
> >  
> >  static const struct inode_operations ramfs_dir_inode_operations = {
> > -- 
> > 2.34.1