Re: [PATCH v7 2/6] ocfs2: Switch to security_inode_init_security()

[Joseph Qi]

Hi,

Sorry for the late reply.

I don't have much background on this thread. It seems that we have to
check EOPNOTSUPP since ocfs2_init_security_get() may return EOPNOTSUPP
if it doesn't support extended attribute feature for backward
compatibility.

Other looks good. So with above comments addressed, you can add:
Acked-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>

On 1/10/23 4:55 PM, Roberto Sassu wrote:
> On Thu, 2022-12-01 at 11:41 +0100, Roberto Sassu wrote:
>> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>>
>> In preparation for removing security_old_inode_init_security(), switch to
>> security_inode_init_security().
>>
>> Extend the existing ocfs2_initxattrs() to take the
>> ocfs2_security_xattr_info structure from fs_info, and populate the
>> name/value/len triple with the first xattr provided by LSMs.
> 
> Hi Mark, Joel, Joseph
> 
> some time ago I sent this patch set to switch to the newer
> function security_inode_init_security(). Almost all the other parts of
> this patch set have been reviewed, and the patch set itself should be
> ready to be merged.
> 
> I kindly ask if you could have a look at this patch and give your
> Reviewed-by, so that Paul could take the patch set.
> 
> Thanks a lot!
> 
> Roberto
> 
>> As fs_info was not used before, ocfs2_initxattrs() can now handle the case
>> of replicating the behavior of security_old_inode_init_security(), i.e.
>> just obtaining the xattr, in addition to setting all xattrs provided by
>> LSMs.
>>
>> Supporting multiple xattrs is not currently supported where
>> security_old_inode_init_security() was called (mknod, symlink), as it
>> requires non-trivial changes that can be done at a later time. Like for
>> reiserfs, even if EVM is invoked, it will not provide an xattr (if it is
>> not the first to set it, its xattr will be discarded; if it is the first,
>> it does not have xattrs to calculate the HMAC on).
>>
>> Finally, modify the handling of the return value from
>> ocfs2_init_security_get(). As security_inode_init_security() does not
>> return -EOPNOTSUPP, remove this case and directly handle the error if the
>> return value is not zero.
>>
>> However, the previous case of receiving -EOPNOTSUPP should be still
>> taken into account, as security_inode_init_security() could return zero
>> without setting xattrs and ocfs2 would consider it as if the xattr was set.
>>
>> Instead, if security_inode_init_security() returned zero, look at the xattr
>> if it was set, and behave accordingly, i.e. set si->enable to zero to
>> notify to the functions following ocfs2_init_security_get() that the xattr
>> is not available (same as if security_old_inode_init_security() returned
>> -EOPNOTSUPP).
>>
>> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>> Reviewed-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
>> ---
>>  fs/ocfs2/namei.c | 18 ++++++------------
>>  fs/ocfs2/xattr.c | 30 ++++++++++++++++++++++++++----
>>  2 files changed, 32 insertions(+), 16 deletions(-)
>>
>> diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
>> index 05f32989bad6..55fba81cd2d1 100644
>> --- a/fs/ocfs2/namei.c
>> +++ b/fs/ocfs2/namei.c
>> @@ -242,6 +242,7 @@ static int ocfs2_mknod(struct user_namespace *mnt_userns,
>>  	int want_meta = 0;
>>  	int xattr_credits = 0;
>>  	struct ocfs2_security_xattr_info si = {
>> +		.name = NULL,
>>  		.enable = 1,
>>  	};
>>  	int did_quota_inode = 0;
>> @@ -315,12 +316,8 @@ static int ocfs2_mknod(struct user_namespace *mnt_userns,
>>  	/* get security xattr */
>>  	status = ocfs2_init_security_get(inode, dir, &dentry->d_name, &si);
>>  	if (status) {
>> -		if (status == -EOPNOTSUPP)
>> -			si.enable = 0;
>> -		else {
>> -			mlog_errno(status);
>> -			goto leave;
>> -		}
>> +		mlog_errno(status);
>> +		goto leave;
>>  	}
>>  
>>  	/* calculate meta data/clusters for setting security and acl xattr */
>> @@ -1805,6 +1802,7 @@ static int ocfs2_symlink(struct user_namespace *mnt_userns,
>>  	int want_clusters = 0;
>>  	int xattr_credits = 0;
>>  	struct ocfs2_security_xattr_info si = {
>> +		.name = NULL,
>>  		.enable = 1,
>>  	};
>>  	int did_quota = 0, did_quota_inode = 0;
>> @@ -1875,12 +1873,8 @@ static int ocfs2_symlink(struct user_namespace *mnt_userns,
>>  	/* get security xattr */
>>  	status = ocfs2_init_security_get(inode, dir, &dentry->d_name, &si);
>>  	if (status) {
>> -		if (status == -EOPNOTSUPP)
>> -			si.enable = 0;
>> -		else {
>> -			mlog_errno(status);
>> -			goto bail;
>> -		}
>> +		mlog_errno(status);
>> +		goto bail;
>>  	}
>>  
>>  	/* calculate meta data/clusters for setting security xattr */
>> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
>> index 95d0611c5fc7..55699c573541 100644
>> --- a/fs/ocfs2/xattr.c
>> +++ b/fs/ocfs2/xattr.c
>> @@ -7259,9 +7259,21 @@ static int ocfs2_xattr_security_set(const struct xattr_handler *handler,
>>  static int ocfs2_initxattrs(struct inode *inode, const struct xattr *xattr_array,
>>  		     void *fs_info)
>>  {
>> +	struct ocfs2_security_xattr_info *si = fs_info;
>>  	const struct xattr *xattr;
>>  	int err = 0;
>>  
>> +	if (si) {
>> +		si->value = kmemdup(xattr_array->value, xattr_array->value_len,
>> +				    GFP_KERNEL);
>> +		if (!si->value)
>> +			return -ENOMEM;
>> +
>> +		si->name = xattr_array->name;
>> +		si->value_len = xattr_array->value_len;
>> +		return 0;
>> +	}
>> +
>>  	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
>>  		err = ocfs2_xattr_set(inode, OCFS2_XATTR_INDEX_SECURITY,
>>  				      xattr->name, xattr->value,
>> @@ -7277,13 +7289,23 @@ int ocfs2_init_security_get(struct inode *inode,
>>  			    const struct qstr *qstr,
>>  			    struct ocfs2_security_xattr_info *si)
>>  {
>> +	int ret;
>> +
>>  	/* check whether ocfs2 support feature xattr */
>>  	if (!ocfs2_supports_xattr(OCFS2_SB(dir->i_sb)))
>>  		return -EOPNOTSUPP;
>> -	if (si)
>> -		return security_old_inode_init_security(inode, dir, qstr,
>> -							&si->name, &si->value,
>> -							&si->value_len);
>> +	if (si) {
>> +		ret = security_inode_init_security(inode, dir, qstr,
>> +						   &ocfs2_initxattrs, si);
>> +		/*
>> +		 * security_inode_init_security() does not return -EOPNOTSUPP,
>> +		 * we have to check the xattr ourselves.
>> +		 */
>> +		if (!ret && !si->name)
>> +			si->enable = 0;
>> +
>> +		return ret;
>> +	}
>>  
>>  	return security_inode_init_security(inode, dir, qstr,
>>  					    &ocfs2_initxattrs, NULL);