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
   8 static 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
  23 static 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
  67 static 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);
 121 skip_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
 136 const struct file_operations erofs_dir_fops = {
 137         .llseek         = generic_file_llseek,
 138         .read           = generic_read_dir,
 139         .iterate_shared = erofs_readdir,
 140 };