Re: [RFC PATCH v3 1/5] UBIFS: ACL: introduce init/set/get functions for ACL

[Dongsheng Yang <yangds.fnst@cn.fujitsu.com>]

On 09/11/2015 05:09 PM, Sheng Yong wrote:
> This patch introduce a new file `acl.c', which implements:
>    * initializing ACL for new file according to the directory's default ACL,
>    * getting ACL which finds the ACL releated xattr and converts it to ACL,
>    * setting ACL function which converts ACL to xattr and creates/changes/
>      removes the xattr.
>
> On flash ACL format is based on POSIX ACL structures, and POSIX generic
> functions, posix_acl_[to|from]_xattr, are called to do the ACL conversion
> between in-memory and on-flash ACL.
>
> The ACL xattr handler is not implemented, because UBIFS does not use it.

Why not, I think we can use it.

Yang
>
> Signed-off-by: Sheng Yong <shengyong1@huawei.com>
> ---
>   fs/ubifs/acl.c   | 141 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   fs/ubifs/ubifs.h |  14 ++++++
>   2 files changed, 155 insertions(+)
>   create mode 100644 fs/ubifs/acl.c
>
> diff --git a/fs/ubifs/acl.c b/fs/ubifs/acl.c
> new file mode 100644
> index 0000000..bf37875
> --- /dev/null
> +++ b/fs/ubifs/acl.c
> @@ -0,0 +1,141 @@
> +/*
> + * This file is part of UBIFS.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + */
> +
> +#include <linux/fs.h>
> +#include <linux/xattr.h>
> +#include <linux/posix_acl_xattr.h>
> +
> +#include "ubifs.h"
> +
> +struct posix_acl *ubifs_get_acl(struct inode *inode, int type)
> +{
> +	struct posix_acl *acl;
> +	char *name, *value = NULL;
> +	int size = 0;
> +
> +	switch (type) {
> +	case ACL_TYPE_ACCESS:
> +		name = XATTR_NAME_POSIX_ACL_ACCESS;
> +		break;
> +	case ACL_TYPE_DEFAULT:
> +		name = XATTR_NAME_POSIX_ACL_DEFAULT;
> +		break;
> +	default:
> +		BUG();
> +	}
> +
> +	size = ubifs_do_getxattr(inode, name, NULL, 0);
> +	if (size > 0) {
> +		value = kmalloc(size, GFP_KERNEL);
> +		if (!value)
> +			return ERR_PTR(-ENOMEM);
> +		size = ubifs_do_getxattr(inode, name, value, size);
> +	}
> +	if (size > 0)
> +		acl = posix_acl_from_xattr(&init_user_ns, value, size);
> +	else if (size == -ENODATA)
> +		acl = NULL;
> +	else
> +		acl = ERR_PTR(size);
> +
> +	kfree(value);
> +	if (!IS_ERR(acl))
> +		set_cached_acl(inode, type, acl);
> +
> +	return acl;
> +}
> +
> +int ubifs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
> +{
> +	char *name;
> +	void *value = NULL;
> +	size_t size = 0;
> +	int flag = 0, err;
> +
> +	switch (type) {
> +	case ACL_TYPE_ACCESS:
> +		name = XATTR_NAME_POSIX_ACL_ACCESS;
> +		if (acl) {
> +			err = posix_acl_equiv_mode(acl, &inode->i_mode);
> +			if (err < 0)
> +				return err;
> +			if (err == 0)
> +				acl = NULL;
> +		}
> +		break;
> +
> +	case ACL_TYPE_DEFAULT:
> +		name = XATTR_NAME_POSIX_ACL_DEFAULT;
> +		if (!S_ISDIR(inode->i_mode))
> +			return acl ? -EACCES : 0;
> +		break;
> +
> +	default:
> +		BUG();
> +	}
> +
> +	if (acl) {
> +		size = posix_acl_xattr_size(acl->a_count);
> +		value = kmalloc(size, GFP_NOFS);
> +		if (!value)
> +			return -ENOMEM;
> +
> +		err = posix_acl_to_xattr(&init_user_ns, acl, value, size);
> +		if (err < 0) {
> +			kfree(value);
> +			return err;
> +		}
> +	}
> +
> +	if (size == 0)
> +		flag = XATTR_REPLACE;
> +	err = ubifs_do_setxattr(inode, name, value, size, flag);
> +
> +	kfree(value);
> +	if (!err)
> +		set_cached_acl(inode, type, acl);
> +
> +	return err;
> +}
> +
> +/*
> + * Initialize the ACLs of a new inode.
> + */
> +int ubifs_init_acl(struct inode *dir, struct inode *inode)
> +{
> +	struct posix_acl *default_acl, *acl;
> +	int err;
> +
> +	err = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
> +	if (err)
> +		return err;
> +
> +	if (default_acl) {
> +		mutex_lock(&inode->i_mutex);
> +		err = ubifs_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
> +		mutex_unlock(&inode->i_mutex);
> +		posix_acl_release(default_acl);
> +	}
> +
> +	if (acl) {
> +		if (!err) {
> +			mutex_lock(&inode->i_mutex);
> +			err = ubifs_set_acl(inode, acl, ACL_TYPE_ACCESS);
> +			mutex_unlock(&inode->i_mutex);
> +		}
> +		posix_acl_release(acl);
> +	}
> +
> +	return err;
> +}
> diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
> index 62aa1a5..b9ddc8d 100644
> --- a/fs/ubifs/ubifs.h
> +++ b/fs/ubifs/ubifs.h
> @@ -1767,6 +1767,20 @@ int ubifs_removexattr(struct dentry *dentry, const char *name);
>   int ubifs_init_security(struct inode *dentry, struct inode *inode,
>   			const struct qstr *qstr);
>
> +/* acl.c */
> +#ifdef CONFIG_UBIFS_FS_POSIX_ACL
> +int ubifs_init_acl(struct inode *dir, struct inode *inode);
> +int ubifs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
> +struct posix_acl *ubifs_get_acl(struct inode *inode, int type);
> +#else
> +static inline int ubifs_init_acl(struct inode *inode, struct inode *dir)
> +{
> +	return 0;
> +}
> +#define ubifs_get_acl NULL
> +#define ubifs_set_acl NULL
> +#endif
> +
>   /* super.c */
>   struct inode *ubifs_iget(struct super_block *sb, unsigned long inum);
>
>