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

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Date: Fri, 26 Jan 2024 08:27:54 -0800
From: Casey Schaufler <casey@...aufler-ca.com>
To: Roberto Sassu <roberto.sassu@...weicloud.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: 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>,
 Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v3 5/5] ramfs: Initialize security of in-memory inodes

On 1/25/2024 11:53 PM, Roberto Sassu wrote:
> 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.

I will take this in the Smack tree. Thank you.

> 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
>