staging/erofs/xattr.c

// SPDX-License-Identifier: GPL-2.0
/*
 * linux/drivers/staging/erofs/xattr.c
 *
 * Copyright (C) 2017-2018 HUAWEI, Inc.
 *             http://www.huawei.com/
 * Created by Gao Xiang <gaoxiang25@huawei.com>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file COPYING in the main directory of the Linux
 * distribution for more details.
 */
#include <linux/security.h>
#include "xattr.h"

struct xattr_iter {
	struct super_block *sb;
	struct page *page;
	void *kaddr;

	erofs_blk_t blkaddr;
	unsigned ofs;
};

static inline void xattr_iter_end(struct xattr_iter *it, bool atomic)
{
	/* only init_inode_xattrs use non-atomic once */
	if (unlikely(!atomic))
		kunmap(it->page);
	else
		kunmap_atomic(it->kaddr);
	unlock_page(it->page);
	put_page(it->page);
}

static void init_inode_xattrs(struct inode *inode)
{
	struct xattr_iter it;
	unsigned i;
	struct erofs_xattr_ibody_header *ih;
	struct erofs_sb_info *sbi;
	struct erofs_vnode *vi;
	bool atomic_map;

	if (likely(inode_has_inited_xattr(inode)))
		return;

	vi = EROFS_V(inode);
	BUG_ON(!vi->xattr_isize);

	sbi = EROFS_I_SB(inode);
	it.blkaddr = erofs_blknr(iloc(sbi, vi->nid) + vi->inode_isize);
	it.ofs = erofs_blkoff(iloc(sbi, vi->nid) + vi->inode_isize);

	it.page = erofs_get_inline_page(inode, it.blkaddr);
	BUG_ON(IS_ERR(it.page));

	/* read in shared xattr array (non-atomic, see kmalloc below) */
	it.kaddr = kmap(it.page);
	atomic_map = false;

	ih = (struct erofs_xattr_ibody_header *)(it.kaddr + it.ofs);

	vi->xattr_shared_count = ih->h_shared_count;
	vi->xattr_shared_xattrs = (unsigned *)kmalloc_array(
		vi->xattr_shared_count, sizeof(unsigned),
		GFP_KERNEL | __GFP_NOFAIL);

	/* let's skip ibody header */
	it.ofs += sizeof(struct erofs_xattr_ibody_header);

	for (i = 0; i < vi->xattr_shared_count; ++i) {
		if (unlikely(it.ofs >= EROFS_BLKSIZ)) {
			/* cannot be unaligned */
			BUG_ON(it.ofs != EROFS_BLKSIZ);
			xattr_iter_end(&it, atomic_map);

			it.page = erofs_get_meta_page(inode->i_sb,
				++it.blkaddr, S_ISDIR(inode->i_mode));
			BUG_ON(IS_ERR(it.page));

			it.kaddr = kmap_atomic(it.page);
			atomic_map = true;
			it.ofs = 0;
		}
		vi->xattr_shared_xattrs[i] =
			le32_to_cpu(*(__le32 *)(it.kaddr + it.ofs));
		it.ofs += sizeof(__le32);
	}
	xattr_iter_end(&it, atomic_map);

	inode_set_inited_xattr(inode);
}

struct xattr_iter_handlers {
	int (*entry)(struct xattr_iter *, struct erofs_xattr_entry *);
	int (*name)(struct xattr_iter *, unsigned, char *, unsigned);
	int (*alloc_buffer)(struct xattr_iter *, unsigned);
	void (*value)(struct xattr_iter *, unsigned, char *, unsigned);
};

static void xattr_iter_fixup(struct xattr_iter *it)
{
	if (unlikely(it->ofs >= EROFS_BLKSIZ)) {
		xattr_iter_end(it, true);

		it->blkaddr += erofs_blknr(it->ofs);
		it->page = erofs_get_meta_page(it->sb, it->blkaddr, false);
		BUG_ON(IS_ERR(it->page));

		it->kaddr = kmap_atomic(it->page);
		it->ofs = erofs_blkoff(it->ofs);
	}
}

static int inline_xattr_iter_begin(struct xattr_iter *it,
	struct inode *inode)
{
	struct erofs_vnode *const vi = EROFS_V(inode);
	struct erofs_sb_info *const sbi = EROFS_SB(inode->i_sb);
	unsigned xattr_header_sz, inline_xattr_ofs;

	xattr_header_sz = inlinexattr_header_size(inode);
	if (unlikely(xattr_header_sz >= vi->xattr_isize)) {
		BUG_ON(xattr_header_sz > vi->xattr_isize);
		return -ENOATTR;
	}

	inline_xattr_ofs = vi->inode_isize + xattr_header_sz;

	it->blkaddr = erofs_blknr(iloc(sbi, vi->nid) + inline_xattr_ofs);
	it->ofs = erofs_blkoff(iloc(sbi, vi->nid) + inline_xattr_ofs);

	it->page = erofs_get_inline_page(inode, it->blkaddr);
	BUG_ON(IS_ERR(it->page));
	it->kaddr = kmap_atomic(it->page);

	return vi->xattr_isize - xattr_header_sz;
}

static int xattr_foreach(struct xattr_iter *it,
	struct xattr_iter_handlers *op, unsigned *tlimit)
{
	struct erofs_xattr_entry entry;
	unsigned value_sz, processed, slice;
	int err;

	/* 0. fixup blkaddr, ofs, ipage */
	xattr_iter_fixup(it);

	/*
	 * 1. read xattr entry to the memory,
	 *    since we do EROFS_XATTR_ALIGN
	 *    therefore entry should be in the page
	 */
	entry = *(struct erofs_xattr_entry *)(it->kaddr + it->ofs);
	if (tlimit != NULL) {
		unsigned entry_sz = EROFS_XATTR_ENTRY_SIZE(&entry);

		BUG_ON(*tlimit < entry_sz);
		*tlimit -= entry_sz;
	}

	it->ofs += sizeof(struct erofs_xattr_entry);
	value_sz = le16_to_cpu(entry.e_value_size);

	/* handle entry */
	err = op->entry(it, &entry);
	if (err) {
		it->ofs += entry.e_name_len + value_sz;
		goto out;
	}

	/* 2. handle xattr name (ofs will finally be at the end of name) */
	processed = 0;

	while (processed < entry.e_name_len) {
		if (it->ofs >= EROFS_BLKSIZ) {
			BUG_ON(it->ofs > EROFS_BLKSIZ);

			xattr_iter_fixup(it);
			it->ofs = 0;
		}

		slice = min_t(unsigned, PAGE_SIZE - it->ofs,
			entry.e_name_len - processed);

		/* handle name */
		err = op->name(it, processed, it->kaddr + it->ofs, slice);
		if (err) {
			it->ofs += entry.e_name_len - processed + value_sz;
			goto out;
		}

		it->ofs += slice;
		processed += slice;
	}

	/* 3. handle xattr value */
	processed = 0;

	if (op->alloc_buffer != NULL) {
		err = op->alloc_buffer(it, value_sz);
		if (err) {
			it->ofs += value_sz;
			goto out;
		}
	}

	while (processed < value_sz) {
		if (it->ofs >= EROFS_BLKSIZ) {
			BUG_ON(it->ofs > EROFS_BLKSIZ);
			xattr_iter_fixup(it);
			it->ofs = 0;
		}

		slice = min_t(unsigned, PAGE_SIZE - it->ofs,
			value_sz - processed);
		op->value(it, processed, it->kaddr + it->ofs, slice);
		it->ofs += slice;
		processed += slice;
	}

out:
	/* we assume that ofs is aligned with 4 bytes */
	it->ofs = EROFS_XATTR_ALIGN(it->ofs);
	return err;
}

struct getxattr_iter {
	struct xattr_iter it;

	char *buffer;
	int buffer_size, index;
	struct qstr name;
};

static int xattr_entrymatch(struct xattr_iter *_it,
	struct erofs_xattr_entry *entry)
{
	struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);

	return (it->index != entry->e_name_index ||
		it->name.len != entry->e_name_len) ? -ENOATTR : 0;
}

static int xattr_namematch(struct xattr_iter *_it,
	unsigned processed, char *buf, unsigned len)
{
	struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);

	return memcmp(buf, it->name.name + processed, len) ? -ENOATTR : 0;
}

static int xattr_checkbuffer(struct xattr_iter *_it,
	unsigned value_sz)
{
	struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);
	int err = it->buffer_size < value_sz ? -ERANGE : 0;

	it->buffer_size = value_sz;
	return it->buffer == NULL ? 1 : err;
}

static void xattr_copyvalue(struct xattr_iter *_it,
	unsigned processed, char *buf, unsigned len)
{
	struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);

	memcpy(it->buffer + processed, buf, len);
}

static struct xattr_iter_handlers find_xattr_handlers = {
	.entry = xattr_entrymatch,
	.name = xattr_namematch,
	.alloc_buffer = xattr_checkbuffer,
	.value = xattr_copyvalue
};

static int inline_getxattr(struct inode *inode, struct getxattr_iter *it)
{
	int ret;
	unsigned remaining;

	ret = inline_xattr_iter_begin(&it->it, inode);
	if (ret < 0)
		return ret;

	remaining = ret;
	while (remaining) {
		ret = xattr_foreach(&it->it, &find_xattr_handlers, &remaining);
		if (ret >= 0)
			break;
	}
	xattr_iter_end(&it->it, true);

	return ret < 0 ? ret : it->buffer_size;
}

static int shared_getxattr(struct inode *inode, struct getxattr_iter *it)
{
	struct erofs_vnode *const vi = EROFS_V(inode);
	struct erofs_sb_info *const sbi = EROFS_SB(inode->i_sb);
	unsigned i;
	int ret = -ENOATTR;

	for (i = 0; i < vi->xattr_shared_count; ++i) {
		erofs_blk_t blkaddr =
			xattrblock_addr(sbi, vi->xattr_shared_xattrs[i]);

		it->it.ofs = xattrblock_offset(sbi, vi->xattr_shared_xattrs[i]);

		if (!i || blkaddr != it->it.blkaddr) {
			if (i)
				xattr_iter_end(&it->it, true);

			it->it.page = erofs_get_meta_page(inode->i_sb,
				blkaddr, false);
			BUG_ON(IS_ERR(it->it.page));
			it->it.kaddr = kmap_atomic(it->it.page);
			it->it.blkaddr = blkaddr;
		}

		ret = xattr_foreach(&it->it, &find_xattr_handlers, NULL);
		if (ret >= 0)
			break;
	}
	if (vi->xattr_shared_count)
		xattr_iter_end(&it->it, true);

	return ret < 0 ? ret : it->buffer_size;
}

static bool erofs_xattr_user_list(struct dentry *dentry)
{
	return test_opt(EROFS_SB(dentry->d_sb), XATTR_USER);
}

static bool erofs_xattr_trusted_list(struct dentry *dentry)
{
	return capable(CAP_SYS_ADMIN);
}

int erofs_getxattr(struct inode *inode, int index,
	const char *name,
	void *buffer, size_t buffer_size)
{
	int ret;
	struct getxattr_iter it;

	if (unlikely(name == NULL))
		return -EINVAL;

	init_inode_xattrs(inode);

	it.index = index;

	it.name.len = strlen(name);
	if (it.name.len > EROFS_NAME_LEN)
		return -ERANGE;
	it.name.name = name;

	it.buffer = buffer;
	it.buffer_size = buffer_size;

	it.it.sb = inode->i_sb;
	ret = inline_getxattr(inode, &it);
	if (ret == -ENOATTR)
		ret = shared_getxattr(inode, &it);
	return ret;
}

static int erofs_xattr_generic_get(const struct xattr_handler *handler,
		struct dentry *unused, struct inode *inode,
		const char *name, void *buffer, size_t size)
{
	struct erofs_vnode *const vi = EROFS_V(inode);
	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);

	switch (handler->flags) {
	case EROFS_XATTR_INDEX_USER:
		if (!test_opt(sbi, XATTR_USER))
			return -EOPNOTSUPP;
		break;
	case EROFS_XATTR_INDEX_TRUSTED:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		break;
	case EROFS_XATTR_INDEX_SECURITY:
		break;
	default:
		return -EINVAL;
	}

	if (!vi->xattr_isize)
		return -ENOATTR;

	return erofs_getxattr(inode, handler->flags, name, buffer, size);
}

const struct xattr_handler erofs_xattr_user_handler = {
	.prefix	= XATTR_USER_PREFIX,
	.flags	= EROFS_XATTR_INDEX_USER,
	.list	= erofs_xattr_user_list,
	.get	= erofs_xattr_generic_get,
};

const struct xattr_handler erofs_xattr_trusted_handler = {
	.prefix	= XATTR_TRUSTED_PREFIX,
	.flags	= EROFS_XATTR_INDEX_TRUSTED,
	.list	= erofs_xattr_trusted_list,
	.get	= erofs_xattr_generic_get,
};

#ifdef CONFIG_EROFS_FS_SECURITY
const struct xattr_handler __maybe_unused erofs_xattr_security_handler = {
	.prefix	= XATTR_SECURITY_PREFIX,
	.flags	= EROFS_XATTR_INDEX_SECURITY,
	.get	= erofs_xattr_generic_get,
};
#endif

const struct xattr_handler *erofs_xattr_handlers[] = {
	&erofs_xattr_user_handler,
#ifdef CONFIG_EROFS_FS_POSIX_ACL
	&posix_acl_access_xattr_handler,
	&posix_acl_default_xattr_handler,
#endif
	&erofs_xattr_trusted_handler,
#ifdef CONFIG_EROFS_FS_SECURITY
	&erofs_xattr_security_handler,
#endif
	NULL,
};

struct listxattr_iter {
	struct xattr_iter it;

	struct dentry *dentry;
	char *buffer;
	int buffer_size, buffer_ofs;
};

static int xattr_entrylist(struct xattr_iter *_it,
	struct erofs_xattr_entry *entry)
{
	struct listxattr_iter *it =
		container_of(_it, struct listxattr_iter, it);
	unsigned prefix_len;
	const char *prefix;

	const struct xattr_handler *h =
		erofs_xattr_handler(entry->e_name_index);

	if (h == NULL || (h->list != NULL && !h->list(it->dentry)))
		return 1;

	/* Note that at least one of 'prefix' and 'name' should be non-NULL */
	prefix = h->prefix != NULL ? h->prefix : h->name;
	prefix_len = strlen(prefix);

	if (it->buffer == NULL) {
		it->buffer_ofs += prefix_len + entry->e_name_len + 1;
		return 1;
	}

	if (it->buffer_ofs + prefix_len
		+ entry->e_name_len + 1 > it->buffer_size)
		return -ERANGE;

	memcpy(it->buffer + it->buffer_ofs, prefix, prefix_len);
	it->buffer_ofs += prefix_len;
	return 0;
}

static int xattr_namelist(struct xattr_iter *_it,
	unsigned processed, char *buf, unsigned len)
{
	struct listxattr_iter *it =
		container_of(_it, struct listxattr_iter, it);

	memcpy(it->buffer + it->buffer_ofs, buf, len);
	it->buffer_ofs += len;
	return 0;
}

static int xattr_skipvalue(struct xattr_iter *_it,
	unsigned value_sz)
{
	struct listxattr_iter *it =
		container_of(_it, struct listxattr_iter, it);

	it->buffer[it->buffer_ofs++] = '\0';
	return 1;
}

static struct xattr_iter_handlers list_xattr_handlers = {
	.entry = xattr_entrylist,
	.name = xattr_namelist,
	.alloc_buffer = xattr_skipvalue,
	.value = NULL
};

static int inline_listxattr(struct listxattr_iter *it)
{
	int ret;
	unsigned remaining;

	ret = inline_xattr_iter_begin(&it->it, d_inode(it->dentry));
	if (ret < 0)
		return ret;

	remaining = ret;
	while (remaining) {
		ret = xattr_foreach(&it->it, &list_xattr_handlers, &remaining);
		if (ret < 0)
			break;
	}
	xattr_iter_end(&it->it, true);
	return ret < 0 ? ret : it->buffer_ofs;
}

static int shared_listxattr(struct listxattr_iter *it)
{
	struct inode *const inode = d_inode(it->dentry);
	struct erofs_vnode *const vi = EROFS_V(inode);
	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
	unsigned i;
	int ret = 0;

	for (i = 0; i < vi->xattr_shared_count; ++i) {
		erofs_blk_t blkaddr =
			xattrblock_addr(sbi, vi->xattr_shared_xattrs[i]);

		it->it.ofs = xattrblock_offset(sbi, vi->xattr_shared_xattrs[i]);
		if (!i || blkaddr != it->it.blkaddr) {
			if (i)
				xattr_iter_end(&it->it, true);

			it->it.page = erofs_get_meta_page(inode->i_sb,
				blkaddr, false);
			BUG_ON(IS_ERR(it->it.page));
			it->it.kaddr = kmap_atomic(it->it.page);
			it->it.blkaddr = blkaddr;
		}

		ret = xattr_foreach(&it->it, &list_xattr_handlers, NULL);
		if (ret < 0)
			break;
	}
	if (vi->xattr_shared_count)
		xattr_iter_end(&it->it, true);

	return ret < 0 ? ret : it->buffer_ofs;
}

ssize_t erofs_listxattr(struct dentry *dentry,
	char *buffer, size_t buffer_size)
{
	int ret;
	struct listxattr_iter it;

	init_inode_xattrs(d_inode(dentry));

	it.dentry = dentry;
	it.buffer = buffer;
	it.buffer_size = buffer_size;
	it.buffer_ofs = 0;

	it.it.sb = dentry->d_sb;

	ret = inline_listxattr(&it);
	if (ret < 0 && ret != -ENOATTR)
		return ret;
	return shared_listxattr(&it);
}