// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/ext4/dir.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/dir.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext4 directory handling functions
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 *
 * Hash Tree Directory indexing (c) 2001  Daniel Phillips
 *
 */

#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/iversion.h>
#include <linux/unicode.h>
#include "ext4.h"
#include "xattr.h"

static int ext4_dx_readdir(struct file *, struct dir_context *);

/**
 * is_dx_dir() - check if a directory is using htree indexing
 * @inode: directory inode
 *
 * Check if the given dir-inode refers to an htree-indexed directory
 * (or a directory which could potentially get converted to use htree
 * indexing).
 *
 * Return 1 if it is a dx dir, 0 if not
 */
static int is_dx_dir(struct inode *inode)
{
        struct super_block *sb = inode->i_sb;

        if (ext4_has_feature_dir_index(inode->i_sb) &&
            ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
             ((inode->i_size >> sb->s_blocksize_bits) == 1) ||
             ext4_has_inline_data(inode)))
                return 1;

        return 0;
}

static bool is_fake_dir_entry(struct ext4_dir_entry_2 *de)
{
        /* Check if . or .. , or skip if namelen is 0 */
        if ((de->name_len > 0) && (de->name_len <= 2) && (de->name[0] == '.') &&
            (de->name[1] == '.' || de->name[1] == '\0'))
                return true;
        /* Check if this is a csum entry */
        if (de->file_type == EXT4_FT_DIR_CSUM)
                return true;
        return false;
}

/*
 * Return 0 if the directory entry is OK, and 1 if there is a problem
 *
 * Note: this is the opposite of what ext2 and ext3 historically returned...
 *
 * bh passed here can be an inode block or a dir data block, depending
 * on the inode inline data flag.
 */
int __ext4_check_dir_entry(const char *function, unsigned int line,
                           struct inode *dir, struct file *filp,
                           struct ext4_dir_entry_2 *de,
                           struct buffer_head *bh, char *buf, int size,
                           unsigned int offset)
{
        const char *error_msg = NULL;
        const int rlen = ext4_rec_len_from_disk(de->rec_len,
                                                dir->i_sb->s_blocksize);
        const int next_offset = ((char *) de - buf) + rlen;
        bool fake = is_fake_dir_entry(de);
        bool has_csum = ext4_has_metadata_csum(dir->i_sb);

        if (unlikely(rlen < ext4_dir_rec_len(1, fake ? NULL : dir)))
                error_msg = "rec_len is smaller than minimal";
        else if (unlikely(rlen % 4 != 0))
                error_msg = "rec_len % 4 != 0";
        else if (unlikely(rlen < ext4_dir_rec_len(de->name_len,
                                                        fake ? NULL : dir)))
                error_msg = "rec_len is too small for name_len";
        else if (unlikely(next_offset > size))
                error_msg = "directory entry overrun";
        else if (unlikely(next_offset > size - ext4_dir_rec_len(1,
                                                  has_csum ? NULL : dir) &&
                          next_offset != size))
                error_msg = "directory entry too close to block end";
        else if (unlikely(le32_to_cpu(de->inode) >
                        le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
                error_msg = "inode out of bounds";
        else
                return 0;

        if (filp)
                ext4_error_file(filp, function, line, bh->b_blocknr,
                                "bad entry in directory: %s - offset=%u, "
                                "inode=%u, rec_len=%d, size=%d fake=%d",
                                error_msg, offset, le32_to_cpu(de->inode),
                                rlen, size, fake);
        else
                ext4_error_inode(dir, function, line, bh->b_blocknr,
                                "bad entry in directory: %s - offset=%u, "
                                "inode=%u, rec_len=%d, size=%d fake=%d",
                                 error_msg, offset, le32_to_cpu(de->inode),
                                 rlen, size, fake);

        return 1;
}

static int ext4_readdir(struct file *file, struct dir_context *ctx)
{
        unsigned int offset;
        int i;
        struct ext4_dir_entry_2 *de;
        int err;
        struct inode *inode = file_inode(file);
        struct super_block *sb = inode->i_sb;
        struct buffer_head *bh = NULL;
        struct fscrypt_str fstr = FSTR_INIT(NULL, 0);

        err = fscrypt_prepare_readdir(inode);
        if (err)
                return err;

        if (is_dx_dir(inode)) {
                err = ext4_dx_readdir(file, ctx);
                if (err != ERR_BAD_DX_DIR)
                        return err;

                /* Can we just clear INDEX flag to ignore htree information? */
                if (!ext4_has_metadata_csum(sb)) {
                        /*
                         * We don't set the inode dirty flag since it's not
                         * critical that it gets flushed back to the disk.
                         */
                        ext4_clear_inode_flag(inode, EXT4_INODE_INDEX);
                }
        }

        if (ext4_has_inline_data(inode)) {
                int has_inline_data = 1;
                err = ext4_read_inline_dir(file, ctx,
                                           &has_inline_data);
                if (has_inline_data)
                        return err;
        }

        if (IS_ENCRYPTED(inode)) {
                err = fscrypt_fname_alloc_buffer(EXT4_NAME_LEN, &fstr);
                if (err < 0)
                        return err;
        }

        while (ctx->pos < inode->i_size) {
                struct ext4_map_blocks map;

                if (fatal_signal_pending(current)) {
                        err = -ERESTARTSYS;
                        goto errout;
                }
                cond_resched();
                offset = ctx->pos & (sb->s_blocksize - 1);
                map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
                map.m_len = 1;
                err = ext4_map_blocks(NULL, inode, &map, 0);
                if (err == 0) {
                        /* m_len should never be zero but let's avoid
                         * an infinite loop if it somehow is */
                        if (map.m_len == 0)
                                map.m_len = 1;
                        ctx->pos += map.m_len * sb->s_blocksize;
                        continue;
                }
                if (err > 0) {
                        pgoff_t index = map.m_pblk >>
                                        (PAGE_SHIFT - inode->i_blkbits);
                        if (!ra_has_index(&file->f_ra, index))
                                page_cache_sync_readahead(
                                        sb->s_bdev->bd_inode->i_mapping,
                                        &file->f_ra, file,
                                        index, 1);
                        file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
                        bh = ext4_bread(NULL, inode, map.m_lblk, 0);
                        if (IS_ERR(bh)) {
                                err = PTR_ERR(bh);
                                bh = NULL;
                                goto errout;
                        }
                }

                if (!bh) {
                        /* corrupt size?  Maybe no more blocks to read */
                        if (ctx->pos > inode->i_blocks << 9)
                                break;
                        ctx->pos += sb->s_blocksize - offset;
                        continue;
                }

                /* Check the checksum */
                if (!buffer_verified(bh) &&
                    !ext4_dirblock_csum_verify(inode, bh)) {
                        EXT4_ERROR_FILE(file, 0, "directory fails checksum "
                                        "at offset %llu",
                                        (unsigned long long)ctx->pos);
                        ctx->pos += sb->s_blocksize - offset;
                        brelse(bh);
                        bh = NULL;
                        continue;
                }
                set_buffer_verified(bh);

                /* If the dir block has changed since the last call to
                 * readdir(2), then we might be pointing to an invalid
                 * dirent right now.  Scan from the start of the block
                 * to make sure. */
                if (!inode_eq_iversion(inode, file->f_version)) {
                        for (i = 0; i < sb->s_blocksize && i < offset; ) {
                                de = (struct ext4_dir_entry_2 *)
                                        (bh->b_data + i);
                                /* It's too expensive to do a full
                                 * dirent test each time round this
                                 * loop, but we do have to test at
                                 * least that it is non-zero.  A
                                 * failure will be detected in the
                                 * dirent test below. */
                                if (ext4_rec_len_from_disk(de->rec_len,
                                        sb->s_blocksize) < ext4_dir_rec_len(1,
                                                                        inode))
                                        break;
                                i += ext4_rec_len_from_disk(de->rec_len,
                                                            sb->s_blocksize);
                        }
                        offset = i;
                        ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
                                | offset;
                        file->f_version = inode_query_iversion(inode);
                }

                while (ctx->pos < inode->i_size
                       && offset < sb->s_blocksize) {
                        de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
                        if (ext4_check_dir_entry(inode, file, de, bh,
                                                 bh->b_data, bh->b_size,
                                                 offset)) {
                                /*
                                 * On error, skip to the next block
                                 */
                                ctx->pos = (ctx->pos |
                                                (sb->s_blocksize - 1)) + 1;
                                break;
                        }
                        offset += ext4_rec_len_from_disk(de->rec_len,
                                        sb->s_blocksize);
                        if (le32_to_cpu(de->inode)) {
                                if (!IS_ENCRYPTED(inode)) {
                                        if (!dir_emit(ctx, de->name,
                                            de->name_len,
                                            le32_to_cpu(de->inode),
                                            get_dtype(sb, de->file_type)))
                                                goto done;
                                } else {
                                        int save_len = fstr.len;
                                        struct fscrypt_str de_name =
                                                        FSTR_INIT(de->name,
                                                                de->name_len);

                                        /* Directory is encrypted */
                                        err = fscrypt_fname_disk_to_usr(inode,
                                                EXT4_DIRENT_HASH(de),
                                                EXT4_DIRENT_MINOR_HASH(de),
                                                &de_name, &fstr);
                                        de_name = fstr;
                                        fstr.len = save_len;
                                        if (err)
                                                goto errout;
                                        if (!dir_emit(ctx,
                                            de_name.name, de_name.len,
                                            le32_to_cpu(de->inode),
                                            get_dtype(sb, de->file_type)))
                                                goto done;
                                }
                        }
                        ctx->pos += ext4_rec_len_from_disk(de->rec_len,
                                                sb->s_blocksize);
                }
                if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
                        goto done;
                brelse(bh);
                bh = NULL;
                offset = 0;
        }
done:
        err = 0;
errout:
        fscrypt_fname_free_buffer(&fstr);
        brelse(bh);
        return err;
}

static inline int is_32bit_api(void)
{
#ifdef CONFIG_COMPAT
        return in_compat_syscall();
#else
        return (BITS_PER_LONG == 32);
#endif
}

/*
 * These functions convert from the major/minor hash to an f_pos
 * value for dx directories
 *
 * Upper layer (for example NFS) should specify FMODE_32BITHASH or
 * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
 * directly on both 32-bit and 64-bit nodes, under such case, neither
 * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
 */
static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
{
        if ((filp->f_mode & FMODE_32BITHASH) ||
            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
                return major >> 1;
        else
                return ((__u64)(major >> 1) << 32) | (__u64)minor;
}

static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
{
        if ((filp->f_mode & FMODE_32BITHASH) ||
            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
                return (pos << 1) & 0xffffffff;
        else
                return ((pos >> 32) << 1) & 0xffffffff;
}

static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
{
        if ((filp->f_mode & FMODE_32BITHASH) ||
            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
                return 0;
        else
                return pos & 0xffffffff;
}

/*
 * Return 32- or 64-bit end-of-file for dx directories
 */
static inline loff_t ext4_get_htree_eof(struct file *filp)
{
        if ((filp->f_mode & FMODE_32BITHASH) ||
            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
                return EXT4_HTREE_EOF_32BIT;
        else
                return EXT4_HTREE_EOF_64BIT;
}


/*
 * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
 * directories, where the "offset" is in terms of the filename hash
 * value instead of the byte offset.
 *
 * Because we may return a 64-bit hash that is well beyond offset limits,
 * we need to pass the max hash as the maximum allowable offset in
 * the htree directory case.
 *
 * For non-htree, ext4_llseek already chooses the proper max offset.
 */
static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *inode = file->f_mapping->host;
        int dx_dir = is_dx_dir(inode);
        loff_t ret, htree_max = ext4_get_htree_eof(file);

        if (likely(dx_dir))
                ret = generic_file_llseek_size(file, offset, whence,
                                                    htree_max, htree_max);
        else
                ret = ext4_llseek(file, offset, whence);
        file->f_version = inode_peek_iversion(inode) - 1;
        return ret;
}

/*
 * This structure holds the nodes of the red-black tree used to store
 * the directory entry in hash order.
 */
struct fname {
        __u32           hash;
        __u32           minor_hash;
        struct rb_node  rb_hash;
        struct fname    *next;
        __u32           inode;
        __u8            name_len;
        __u8            file_type;
        char            name[];
};

/*
 * This functoin implements a non-recursive way of freeing all of the
 * nodes in the red-black tree.
 */
static void free_rb_tree_fname(struct rb_root *root)
{
        struct fname *fname, *next;

        rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
                while (fname) {
                        struct fname *old = fname;
                        fname = fname->next;
                        kfree(old);
                }

        *root = RB_ROOT;
}


static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
                                                           loff_t pos)
{
        struct dir_private_info *p;

        p = kzalloc(sizeof(*p), GFP_KERNEL);
        if (!p)
                return NULL;
        p->curr_hash = pos2maj_hash(filp, pos);
        p->curr_minor_hash = pos2min_hash(filp, pos);
        return p;
}

void ext4_htree_free_dir_info(struct dir_private_info *p)
{
        free_rb_tree_fname(&p->root);
        kfree(p);
}

/*
 * Given a directory entry, enter it into the fname rb tree.
 *
 * When filename encryption is enabled, the dirent will hold the
 * encrypted filename, while the htree will hold decrypted filename.
 * The decrypted filename is passed in via ent_name.  parameter.
 */
int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
                             __u32 minor_hash,
                            struct ext4_dir_entry_2 *dirent,
                            struct fscrypt_str *ent_name)
{
        struct rb_node **p, *parent = NULL;
        struct fname *fname, *new_fn;
        struct dir_private_info *info;
        int len;

        info = dir_file->private_data;
        p = &info->root.rb_node;

        /* Create and allocate the fname structure */
        len = sizeof(struct fname) + ent_name->len + 1;
        new_fn = kzalloc(len, GFP_KERNEL);
        if (!new_fn)
                return -ENOMEM;
        new_fn->hash = hash;
        new_fn->minor_hash = minor_hash;
        new_fn->inode = le32_to_cpu(dirent->inode);
        new_fn->name_len = ent_name->len;
        new_fn->file_type = dirent->file_type;
        memcpy(new_fn->name, ent_name->name, ent_name->len);

        while (*p) {
                parent = *p;
                fname = rb_entry(parent, struct fname, rb_hash);

                /*
                 * If the hash and minor hash match up, then we put
                 * them on a linked list.  This rarely happens...
                 */
                if ((new_fn->hash == fname->hash) &&
                    (new_fn->minor_hash == fname->minor_hash)) {
                        new_fn->next = fname->next;
                        fname->next = new_fn;
                        return 0;
                }

                if (new_fn->hash < fname->hash)
                        p = &(*p)->rb_left;
                else if (new_fn->hash > fname->hash)
                        p = &(*p)->rb_right;
                else if (new_fn->minor_hash < fname->minor_hash)
                        p = &(*p)->rb_left;
                else /* if (new_fn->minor_hash > fname->minor_hash) */
                        p = &(*p)->rb_right;
        }

        rb_link_node(&new_fn->rb_hash, parent, p);
        rb_insert_color(&new_fn->rb_hash, &info->root);
        return 0;
}



/*
 * This is a helper function for ext4_dx_readdir.  It calls filldir
 * for all entres on the fname linked list.  (Normally there is only
 * one entry on the linked list, unless there are 62 bit hash collisions.)
 */
static int call_filldir(struct file *file, struct dir_context *ctx,
                        struct fname *fname)
{
        struct dir_private_info *info = file->private_data;
        struct inode *inode = file_inode(file);
        struct super_block *sb = inode->i_sb;

        if (!fname) {
                ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
                         "called with null fname?!?", __func__, __LINE__,
                         inode->i_ino, current->comm);
                return 0;
        }
        ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
        while (fname) {
                if (!dir_emit(ctx, fname->name,
                                fname->name_len,
                                fname->inode,
                                get_dtype(sb, fname->file_type))) {
                        info->extra_fname = fname;
                        return 1;
                }
                fname = fname->next;
        }
        return 0;
}

static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
{
        struct dir_private_info *info = file->private_data;
        struct inode *inode = file_inode(file);
        struct fname *fname;
        int ret = 0;

        if (!info) {
                info = ext4_htree_create_dir_info(file, ctx->pos);
                if (!info)
                        return -ENOMEM;
                file->private_data = info;
        }

        if (ctx->pos == ext4_get_htree_eof(file))
                return 0;       /* EOF */

        /* Some one has messed with f_pos; reset the world */
        if (info->last_pos != ctx->pos) {
                free_rb_tree_fname(&info->root);
                info->curr_node = NULL;
                info->extra_fname = NULL;
                info->curr_hash = pos2maj_hash(file, ctx->pos);
                info->curr_minor_hash = pos2min_hash(file, ctx->pos);
        }

        /*
         * If there are any leftover names on the hash collision
         * chain, return them first.
         */
        if (info->extra_fname) {
                if (call_filldir(file, ctx, info->extra_fname))
                        goto finished;
                info->extra_fname = NULL;
                goto next_node;
        } else if (!info->curr_node)
                info->curr_node = rb_first(&info->root);

        while (1) {
                /*
                 * Fill the rbtree if we have no more entries,
                 * or the inode has changed since we last read in the
                 * cached entries.
                 */
                if ((!info->curr_node) ||
                    !inode_eq_iversion(inode, file->f_version)) {
                        info->curr_node = NULL;
                        free_rb_tree_fname(&info->root);
                        file->f_version = inode_query_iversion(inode);
                        ret = ext4_htree_fill_tree(file, info->curr_hash,
                                                   info->curr_minor_hash,
                                                   &info->next_hash);
                        if (ret < 0)
                                goto finished;
                        if (ret == 0) {
                                ctx->pos = ext4_get_htree_eof(file);
                                break;
                        }
                        info->curr_node = rb_first(&info->root);
                }

                fname = rb_entry(info->curr_node, struct fname, rb_hash);
                info->curr_hash = fname->hash;
                info->curr_minor_hash = fname->minor_hash;
                if (call_filldir(file, ctx, fname))
                        break;
        next_node:
                info->curr_node = rb_next(info->curr_node);
                if (info->curr_node) {
                        fname = rb_entry(info->curr_node, struct fname,
                                         rb_hash);
                        info->curr_hash = fname->hash;
                        info->curr_minor_hash = fname->minor_hash;
                } else {
                        if (info->next_hash == ~0) {
                                ctx->pos = ext4_get_htree_eof(file);
                                break;
                        }
                        info->curr_hash = info->next_hash;
                        info->curr_minor_hash = 0;
                }
        }
finished:
        info->last_pos = ctx->pos;
        return ret < 0 ? ret : 0;
}

static int ext4_release_dir(struct inode *inode, struct file *filp)
{
        if (filp->private_data)
                ext4_htree_free_dir_info(filp->private_data);

        return 0;
}

int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
                      int buf_size)
{
        struct ext4_dir_entry_2 *de;
        int rlen;
        unsigned int offset = 0;
        char *top;

        de = (struct ext4_dir_entry_2 *)buf;
        top = buf + buf_size;
        while ((char *) de < top) {
                if (ext4_check_dir_entry(dir, NULL, de, bh,
                                         buf, buf_size, offset))
                        return -EFSCORRUPTED;
                rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
                de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
                offset += rlen;
        }
        if ((char *) de > top)
                return -EFSCORRUPTED;

        return 0;
}

const struct file_operations ext4_dir_operations = {
        .llseek         = ext4_dir_llseek,
        .read           = generic_read_dir,
        .iterate_shared = ext4_readdir,
        .unlocked_ioctl = ext4_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = ext4_compat_ioctl,
#endif
        .fsync          = ext4_sync_file,
        .release        = ext4_release_dir,
};