linux-kernel - Re: [PATCH v6 12/17] securityfs: Extend securityfs with namespacing support

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Date:   Sat, 11 Dec 2021 17:31:36 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     linux-integrity@...r.kernel.org, zohar@...ux.ibm.com,
        serge@...lyn.com, containers@...ts.linux.dev,
        dmitry.kasatkin@...il.com, ebiederm@...ssion.com,
        krzysztof.struczynski@...wei.com, roberto.sassu@...wei.com,
        mpeters@...hat.com, lhinds@...hat.com, lsturman@...hat.com,
        puiterwi@...hat.com, jejb@...ux.ibm.com, jamjoom@...ibm.com,
        linux-kernel@...r.kernel.org, paul@...l-moore.com, rgb@...hat.com,
        linux-security-module@...r.kernel.org, jmorris@...ei.org,
        James Bottomley <James.Bottomley@...senPartnership.com>
Subject: Re: [PATCH v6 12/17] securityfs: Extend securityfs with namespacing
 support


On 12/11/21 05:50, Christian Brauner wrote:
> On Fri, Dec 10, 2021 at 02:47:31PM -0500, Stefan Berger wrote:
>> Extend 'securityfs' for support of IMA namespacing so that each
>> IMA (user) namespace can have its own front-end for showing the currently
>> active policy, the measurement list, number of violations and so on.
>>
>> Drop the addition dentry reference and simplify cleanup to work without
>> the additional reference. This enables simple cleanup of dentries upon
>> umount.
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>> Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
>> ---
>>   security/inode.c | 14 ++++----------
>>   1 file changed, 4 insertions(+), 10 deletions(-)
>>
>> diff --git a/security/inode.c b/security/inode.c
>> index fee01ff4d831..c77ae8ecc464 100644
>> --- a/security/inode.c
>> +++ b/security/inode.c
>> @@ -54,7 +54,7 @@ static int securityfs_fill_super(struct super_block *sb, struct fs_context *fc)
>>   
>>   static int securityfs_get_tree(struct fs_context *fc)
>>   {
>> -	return get_tree_single(fc, securityfs_fill_super);
>> +	return get_tree_keyed(fc, securityfs_fill_super, fc->user_ns);
>>   }
>>   
>>   static const struct fs_context_operations securityfs_context_ops = {
>> @@ -72,6 +72,7 @@ static struct file_system_type fs_type = {
>>   	.name =		"securityfs",
>>   	.init_fs_context = securityfs_init_fs_context,
>>   	.kill_sb =	kill_litter_super,
>> +	.fs_flags =	FS_USERNS_MOUNT,
>>   };
>>   
>>   /**
>> @@ -168,7 +169,6 @@ static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
>>   		inode->i_fop = fops;
>>   	}
>>   	d_instantiate(dentry, inode);
>> -	dget(dentry);
>>   	inode_unlock(dir);
>>   	return dentry;
>>   
>> @@ -306,23 +306,17 @@ EXPORT_SYMBOL_GPL(securityfs_create_symlink);
>>   void securityfs_remove(struct dentry *dentry)
>>   {
>>   	struct user_namespace *ns;
>> -	struct inode *dir;
>>   
>>   	if (!dentry || IS_ERR(dentry))
>>   		return;
>>   
>>   	ns = dentry->d_sb->s_user_ns;
>>   
>> -	dir = d_inode(dentry->d_parent);
>> -	inode_lock(dir);
>>   	if (simple_positive(dentry)) {
>> -		if (d_is_dir(dentry))
>> -			simple_rmdir(dir, dentry);
>> -		else
>> -			simple_unlink(dir, dentry);
>> +		d_delete(dentry);
>>   		dput(dentry);
> In
> https://lore.kernel.org/lkml/20211210114934.tacjnwryihrsx6ln@wittgenstein
> I explained why d_delete()+d_put() only is wrong and how to fix it.


Fixed for v7.