linux-kernel - Re: [PATCH v4 11/16] securityfs: Only use simple_pin_fs/simple_release_fs for init_user

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Date:   Wed, 8 Dec 2021 09:03:43 -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 v4 11/16] securityfs: Only use
 simple_pin_fs/simple_release_fs for init_user_ns


On 12/8/21 06:58, Christian Brauner wrote:
> On Tue, Dec 07, 2021 at 03:21:22PM -0500, Stefan Berger wrote:
>> To prepare for virtualization of SecurityFS, use simple_pin_fs and
>> simpe_release_fs only when init_user_ns is active.
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>> Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
>> ---
>>   security/inode.c | 30 +++++++++++++++++++++---------
>>   1 file changed, 21 insertions(+), 9 deletions(-)
>>
>> diff --git a/security/inode.c b/security/inode.c
>> index 6c326939750d..1a720b2c566d 100644
>> --- a/security/inode.c
>> +++ b/security/inode.c
>> @@ -21,9 +21,10 @@
>>   #include <linux/security.h>
>>   #include <linux/lsm_hooks.h>
>>   #include <linux/magic.h>
>> +#include <linux/user_namespace.h>
>>   
>> -static struct vfsmount *mount;
>> -static int mount_count;
>> +static struct vfsmount *securityfs_mount;
>> +static int securityfs_mount_count;
>>   
>>   static void securityfs_free_inode(struct inode *inode)
>>   {
>> @@ -109,6 +110,7 @@ static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
>>   					const struct file_operations *fops,
>>   					const struct inode_operations *iops)
>>   {
>> +	struct user_namespace *ns = current_user_ns();
>>   	struct dentry *dentry;
>>   	struct inode *dir, *inode;
>>   	int error;
>> @@ -118,12 +120,17 @@ static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
>>   
>>   	pr_debug("securityfs: creating file '%s'\n",name);
>>   
>> -	error = simple_pin_fs(&fs_type, &mount, &mount_count);
>> -	if (error)
>> -		return ERR_PTR(error);
>> +	if (ns == &init_user_ns) {
>> +		error = simple_pin_fs(&fs_type, &securityfs_mount,
>> +				      &securityfs_mount_count);
>> +		if (error)
>> +			return ERR_PTR(error);
>> +	}
>>   
>> -	if (!parent)
>> -		parent = mount->mnt_root;
>> +	if (!parent) {
>> +		if (ns == &init_user_ns)
>> +			parent = securityfs_mount->mnt_root;
> Wouldn't you want an
>
> 		else
> 			return ERR_PTR(-EINVAL);
>
> in here already?


Fixed.