LXR linux/fs/erofs/dir.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (C) 2017-2018 HUAWEI, Inc.
   4 *             https://www.huawei.com/
   5 */
   6#include "internal.h"
   7
   8static void debug_one_dentry(unsigned char d_type, const char *de_name,
   9                             unsigned int de_namelen)
  10{
  11#ifdef CONFIG_EROFS_FS_DEBUG
  12        /* since the on-disk name could not have the trailing '\0' */
  13        unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
  14
  15        memcpy(dbg_namebuf, de_name, de_namelen);
  16        dbg_namebuf[de_namelen] = '\0';
  17
  18        erofs_dbg("found dirent %s de_len %u d_type %d", dbg_namebuf,
  19                  de_namelen, d_type);
  20#endif
  21}
  22
  23static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
  24                               void *dentry_blk, unsigned int *ofs,
  25                               unsigned int nameoff, unsigned int maxsize)
  26{
  27        struct erofs_dirent *de = dentry_blk + *ofs;
  28        const struct erofs_dirent *end = dentry_blk + nameoff;
  29
  30        while (de < end) {
  31                const char *de_name;
  32                unsigned int de_namelen;
  33                unsigned char d_type;
  34
  35                d_type = fs_ftype_to_dtype(de->file_type);
  36
  37                nameoff = le16_to_cpu(de->nameoff);
  38                de_name = (char *)dentry_blk + nameoff;
  39
  40                /* the last dirent in the block? */
  41                if (de + 1 >= end)
  42                        de_namelen = strnlen(de_name, maxsize - nameoff);
  43                else
  44                        de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
  45
  46                /* a corrupted entry is found */
  47                if (nameoff + de_namelen > maxsize ||
  48                    de_namelen > EROFS_NAME_LEN) {
  49                        erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
  50                                  EROFS_I(dir)->nid);
  51                        DBG_BUGON(1);
  52                        return -EFSCORRUPTED;
  53                }
  54
  55                debug_one_dentry(d_type, de_name, de_namelen);
  56                if (!dir_emit(ctx, de_name, de_namelen,
  57                              le64_to_cpu(de->nid), d_type))
  58                        /* stopped by some reason */
  59                        return 1;
  60                ++de;
  61                *ofs += sizeof(struct erofs_dirent);
  62        }
  63        *ofs = maxsize;
  64        return 0;
  65}
  66
  67static int erofs_readdir(struct file *f, struct dir_context *ctx)
  68{
  69        struct inode *dir = file_inode(f);
  70        struct address_space *mapping = dir->i_mapping;
  71        const size_t dirsize = i_size_read(dir);
  72        unsigned int i = ctx->pos / EROFS_BLKSIZ;
  73        unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
  74        int err = 0;
  75        bool initial = true;
  76
  77        while (ctx->pos < dirsize) {
  78                struct page *dentry_page;
  79                struct erofs_dirent *de;
  80                unsigned int nameoff, maxsize;
  81
  82                dentry_page = read_mapping_page(mapping, i, NULL);
  83                if (dentry_page == ERR_PTR(-ENOMEM)) {
  84                        err = -ENOMEM;
  85                        break;
  86                } else if (IS_ERR(dentry_page)) {
  87                        erofs_err(dir->i_sb,
  88                                  "fail to readdir of logical block %u of nid %llu",
  89                                  i, EROFS_I(dir)->nid);
  90                        err = -EFSCORRUPTED;
  91                        break;
  92                }
  93
  94                de = (struct erofs_dirent *)kmap(dentry_page);
  95
  96                nameoff = le16_to_cpu(de->nameoff);
  97
  98                if (nameoff < sizeof(struct erofs_dirent) ||
  99                    nameoff >= PAGE_SIZE) {
 100                        erofs_err(dir->i_sb,
 101                                  "invalid de[0].nameoff %u @ nid %llu",
 102                                  nameoff, EROFS_I(dir)->nid);
 103                        err = -EFSCORRUPTED;
 104                        goto skip_this;
 105                }
 106
 107                maxsize = min_t(unsigned int,
 108                                dirsize - ctx->pos + ofs, PAGE_SIZE);
 109
 110                /* search dirents at the arbitrary position */
 111                if (initial) {
 112                        initial = false;
 113
 114                        ofs = roundup(ofs, sizeof(struct erofs_dirent));
 115                        if (ofs >= nameoff)
 116                                goto skip_this;
 117                }
 118
 119                err = erofs_fill_dentries(dir, ctx, de, &ofs,
 120                                          nameoff, maxsize);
 121skip_this:
 122                kunmap(dentry_page);
 123
 124                put_page(dentry_page);
 125
 126                ctx->pos = blknr_to_addr(i) + ofs;
 127
 128                if (err)
 129                        break;
 130                ++i;
 131                ofs = 0;
 132        }
 133        return err < 0 ? err : 0;
 134}
 135
 136const struct file_operations erofs_dir_fops = {
 137        .llseek         = generic_file_llseek,
 138        .read           = generic_read_dir,
 139        .iterate_shared = erofs_readdir,
 140};
 141