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

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Date: Thu, 25 Jan 2024 17:08:58 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Roberto Sassu <roberto.sassu@...weicloud.com>
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, 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.

> 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