// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2017-2018 HUAWEI, Inc.
 *             https://www.huawei.com/
 */
#include <linux/security.h>
#include "xattr.h"

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

        erofs_blk_t blkaddr;
        unsigned int ofs;
};

static inline void xattr_iter_end(struct xattr_iter *it, bool atomic)
{
        /* the only user of kunmap() is 'init_inode_xattrs' */
        if (!atomic)
                kunmap(it->page);
        else
                kunmap_atomic(it->kaddr);

        unlock_page(it->page);
        put_page(it->page);
}

static inline void xattr_iter_end_final(struct xattr_iter *it)
{
        if (!it->page)
                return;

        xattr_iter_end(it, true);
}

static int init_inode_xattrs(struct inode *inode)
{
        struct erofs_inode *const vi = EROFS_I(inode);
        struct xattr_iter it;
        unsigned int i;
        struct erofs_xattr_ibody_header *ih;
        struct super_block *sb;
        struct erofs_sb_info *sbi;
        bool atomic_map;
        int ret = 0;

        /* the most case is that xattrs of this inode are initialized. */
        if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags)) {
                /*
                 * paired with smp_mb() at the end of the function to ensure
                 * fields will only be observed after the bit is set.
                 */
                smp_mb();
                return 0;
        }

        if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_XATTR_BIT, TASK_KILLABLE))
                return -ERESTARTSYS;

        /* someone has initialized xattrs for us? */
        if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags))
                goto out_unlock;

        /*
         * bypass all xattr operations if ->xattr_isize is not greater than
         * sizeof(struct erofs_xattr_ibody_header), in detail:
         * 1) it is not enough to contain erofs_xattr_ibody_header then
         *    ->xattr_isize should be 0 (it means no xattr);
         * 2) it is just to contain erofs_xattr_ibody_header, which is on-disk
         *    undefined right now (maybe use later with some new sb feature).
         */
        if (vi->xattr_isize == sizeof(struct erofs_xattr_ibody_header)) {
                erofs_err(inode->i_sb,
                          "xattr_isize %d of nid %llu is not supported yet",
                          vi->xattr_isize, vi->nid);
                ret = -EOPNOTSUPP;
                goto out_unlock;
        } else if (vi->xattr_isize < sizeof(struct erofs_xattr_ibody_header)) {
                if (vi->xattr_isize) {
                        erofs_err(inode->i_sb,
                                  "bogus xattr ibody @ nid %llu", vi->nid);
                        DBG_BUGON(1);
                        ret = -EFSCORRUPTED;
                        goto out_unlock;        /* xattr ondisk layout error */
                }
                ret = -ENOATTR;
                goto out_unlock;
        }

        sb = inode->i_sb;
        sbi = EROFS_SB(sb);
        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_meta_page(sb, it.blkaddr);
        if (IS_ERR(it.page)) {
                ret = PTR_ERR(it.page);
                goto out_unlock;
        }

        /* 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 = kmalloc_array(vi->xattr_shared_count,
                                                sizeof(uint), GFP_KERNEL);
        if (!vi->xattr_shared_xattrs) {
                xattr_iter_end(&it, atomic_map);
                ret = -ENOMEM;
                goto out_unlock;
        }

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

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

                        it.page = erofs_get_meta_page(sb, ++it.blkaddr);
                        if (IS_ERR(it.page)) {
                                kfree(vi->xattr_shared_xattrs);
                                vi->xattr_shared_xattrs = NULL;
                                ret = PTR_ERR(it.page);
                                goto out_unlock;
                        }

                        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);

        /* paired with smp_mb() at the beginning of the function. */
        smp_mb();
        set_bit(EROFS_I_EA_INITED_BIT, &vi->flags);

out_unlock:
        clear_and_wake_up_bit(EROFS_I_BL_XATTR_BIT, &vi->flags);
        return ret;
}

/*
 * the general idea for these return values is
 * if    0 is returned, go on processing the current xattr;
 *       1 (> 0) is returned, skip this round to process the next xattr;
 *    -err (< 0) is returned, an error (maybe ENOXATTR) occurred
 *                            and need to be handled
 */
struct xattr_iter_handlers {
        int (*entry)(struct xattr_iter *_it, struct erofs_xattr_entry *entry);
        int (*name)(struct xattr_iter *_it, unsigned int processed, char *buf,
                    unsigned int len);
        int (*alloc_buffer)(struct xattr_iter *_it, unsigned int value_sz);
        void (*value)(struct xattr_iter *_it, unsigned int processed, char *buf,
                      unsigned int len);
};

static inline int xattr_iter_fixup(struct xattr_iter *it)
{
        if (it->ofs < EROFS_BLKSIZ)
                return 0;

        xattr_iter_end(it, true);

        it->blkaddr += erofs_blknr(it->ofs);

        it->page = erofs_get_meta_page(it->sb, it->blkaddr);
        if (IS_ERR(it->page)) {
                int err = PTR_ERR(it->page);

                it->page = NULL;
                return err;
        }

        it->kaddr = kmap_atomic(it->page);
        it->ofs = erofs_blkoff(it->ofs);
        return 0;
}

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

        xattr_header_sz = inlinexattr_header_size(inode);
        if (xattr_header_sz >= vi->xattr_isize) {
                DBG_BUGON(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_meta_page(inode->i_sb, it->blkaddr);
        if (IS_ERR(it->page))
                return PTR_ERR(it->page);

        it->kaddr = kmap_atomic(it->page);
        return vi->xattr_isize - xattr_header_sz;
}

/*
 * Regardless of success or failure, `xattr_foreach' will end up with
 * `ofs' pointing to the next xattr item rather than an arbitrary position.
 */
static int xattr_foreach(struct xattr_iter *it,
                         const struct xattr_iter_handlers *op,
                         unsigned int *tlimit)
{
        struct erofs_xattr_entry entry;
        unsigned int value_sz, processed, slice;
        int err;

        /* 0. fixup blkaddr, ofs, ipage */
        err = xattr_iter_fixup(it);
        if (err)
                return err;

        /*
         * 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) {
                unsigned int entry_sz = erofs_xattr_entry_size(&entry);

                /* xattr on-disk corruption: xattr entry beyond xattr_isize */
                if (*tlimit < entry_sz) {
                        DBG_BUGON(1);
                        return -EFSCORRUPTED;
                }
                *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) {
                        DBG_BUGON(it->ofs > EROFS_BLKSIZ);

                        err = xattr_iter_fixup(it);
                        if (err)
                                goto out;
                        it->ofs = 0;
                }

                slice = min_t(unsigned int, 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) {
                err = op->alloc_buffer(it, value_sz);
                if (err) {
                        it->ofs += value_sz;
                        goto out;
                }
        }

        while (processed < value_sz) {
                if (it->ofs >= EROFS_BLKSIZ) {
                        DBG_BUGON(it->ofs > EROFS_BLKSIZ);

                        err = xattr_iter_fixup(it);
                        if (err)
                                goto out;
                        it->ofs = 0;
                }

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

out:
        /* xattrs should be 4-byte aligned (on-disk constraint) */
        it->ofs = EROFS_XATTR_ALIGN(it->ofs);
        return err < 0 ? err : 0;
}

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 int processed, char *buf, unsigned int 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 int 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 ? 1 : err;
}

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

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

static const 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 int 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 != -ENOATTR)
                        break;
        }
        xattr_iter_end_final(&it->it);

        return ret ? ret : it->buffer_size;
}

static int shared_getxattr(struct inode *inode, struct getxattr_iter *it)
{
        struct erofs_inode *const vi = EROFS_I(inode);
        struct super_block *const sb = inode->i_sb;
        struct erofs_sb_info *const sbi = EROFS_SB(sb);
        unsigned int 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(sb, blkaddr);
                        if (IS_ERR(it->it.page))
                                return PTR_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 != -ENOATTR)
                        break;
        }
        if (vi->xattr_shared_count)
                xattr_iter_end_final(&it->it);

        return ret ? ret : it->buffer_size;
}

static bool erofs_xattr_user_list(struct dentry *dentry)
{
        return test_opt(&EROFS_SB(dentry->d_sb)->ctx, 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 (!name)
                return -EINVAL;

        ret = init_inode_xattrs(inode);
        if (ret)
                return ret;

        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_sb_info *const sbi = EROFS_I_SB(inode);

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

        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 int prefix_len;
        const char *prefix;

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

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

        prefix = xattr_prefix(h);
        prefix_len = strlen(prefix);

        if (!it->buffer) {
                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 int processed, char *buf, unsigned int 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 int value_sz)
{
        struct listxattr_iter *it =
                container_of(_it, struct listxattr_iter, it);

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

static const 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 int 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)
                        break;
        }
        xattr_iter_end_final(&it->it);
        return ret ? ret : it->buffer_ofs;
}

static int shared_listxattr(struct listxattr_iter *it)
{
        struct inode *const inode = d_inode(it->dentry);
        struct erofs_inode *const vi = EROFS_I(inode);
        struct super_block *const sb = inode->i_sb;
        struct erofs_sb_info *const sbi = EROFS_SB(sb);
        unsigned int 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(sb, blkaddr);
                        if (IS_ERR(it->it.page))
                                return PTR_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)
                        break;
        }
        if (vi->xattr_shared_count)
                xattr_iter_end_final(&it->it);

        return ret ? ret : it->buffer_ofs;
}

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

        ret = init_inode_xattrs(d_inode(dentry));
        if (ret == -ENOATTR)
                return 0;
        if (ret)
                return ret;

        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);
}

#ifdef CONFIG_EROFS_FS_POSIX_ACL
struct posix_acl *erofs_get_acl(struct inode *inode, int type, bool rcu)
{
        struct posix_acl *acl;
        int prefix, rc;
        char *value = NULL;

        if (rcu)
                return ERR_PTR(-ECHILD);

        switch (type) {
        case ACL_TYPE_ACCESS:
                prefix = EROFS_XATTR_INDEX_POSIX_ACL_ACCESS;
                break;
        case ACL_TYPE_DEFAULT:
                prefix = EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT;
                break;
        default:
                return ERR_PTR(-EINVAL);
        }

        rc = erofs_getxattr(inode, prefix, "", NULL, 0);
        if (rc > 0) {
                value = kmalloc(rc, GFP_KERNEL);
                if (!value)
                        return ERR_PTR(-ENOMEM);
                rc = erofs_getxattr(inode, prefix, "", value, rc);
        }

        if (rc == -ENOATTR)
                acl = NULL;
        else if (rc < 0)
                acl = ERR_PTR(rc);
        else
                acl = posix_acl_from_xattr(&init_user_ns, value, rc);
        kfree(value);
        return acl;
}
#endif