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

[Roberto Sassu <roberto.sassu@huaweicloud.com>]

On Thu, 2022-12-01 at 11:41 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
> 
> 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@huawei.com>
> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  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);