erofs/dir.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2017-2018 HUAWEI, Inc.
   4  *             http://www.huawei.com/
   5  * Created by Gao Xiang <gaoxiang25@huawei.com>
   6  */
   7 #include "internal.h"
   8
   9 static void debug_one_dentry(unsigned char d_type, const char *de_name,
  10                              unsigned int de_namelen)
  11 {
  12 #ifdef CONFIG_EROFS_FS_DEBUG
  13         /* since the on-disk name could not have the trailing '\0' */
  14         unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
  15
  16         memcpy(dbg_namebuf, de_name, de_namelen);
  17         dbg_namebuf[de_namelen] = '\0';
  18
  19         erofs_dbg("found dirent %s de_len %u d_type %d", dbg_namebuf,
  20                   de_namelen, d_type);
  21 #endif
  22 }
  23
  24 static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
  25                                void *dentry_blk, unsigned int *ofs,
  26                                unsigned int nameoff, unsigned int maxsize)
  27 {
  28         struct erofs_dirent *de = dentry_blk + *ofs;
  29         const struct erofs_dirent *end = dentry_blk + nameoff;
  30
  31         while (de < end) {
  32                 const char *de_name;
  33                 unsigned int de_namelen;
  34                 unsigned char d_type;
  35
  36                 d_type = fs_ftype_to_dtype(de->file_type);
  37
  38                 nameoff = le16_to_cpu(de->nameoff);
  39                 de_name = (char *)dentry_blk + nameoff;
  40
  41                 /* the last dirent in the block? */
  42                 if (de + 1 >= end)
  43                         de_namelen = strnlen(de_name, maxsize - nameoff);
  44                 else
  45                         de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
  46
  47                 /* a corrupted entry is found */
  48                 if (nameoff + de_namelen > maxsize ||
  49                     de_namelen > EROFS_NAME_LEN) {
  50                         erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
  51                                   EROFS_I(dir)->nid);
  52                         DBG_BUGON(1);
  53                         return -EFSCORRUPTED;
  54                 }
  55
  56                 debug_one_dentry(d_type, de_name, de_namelen);
  57                 if (!dir_emit(ctx, de_name, de_namelen,
  58                               le64_to_cpu(de->nid), d_type))
  59                         /* stopped by some reason */
  60                         return 1;
  61                 ++de;
  62                 *ofs += sizeof(struct erofs_dirent);
  63         }
  64         *ofs = maxsize;
  65         return 0;
  66 }
  67
  68 static int erofs_readdir(struct file *f, struct dir_context *ctx)
  69 {
  70         struct inode *dir = file_inode(f);
  71         struct address_space *mapping = dir->i_mapping;
  72         const size_t dirsize = i_size_read(dir);
  73         unsigned int i = ctx->pos / EROFS_BLKSIZ;
  74         unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
  75         int err = 0;
  76         bool initial = true;
  77
  78         while (ctx->pos < dirsize) {
  79                 struct page *dentry_page;
  80                 struct erofs_dirent *de;
  81                 unsigned int nameoff, maxsize;
  82
  83                 dentry_page = read_mapping_page(mapping, i, NULL);
  84                 if (dentry_page == ERR_PTR(-ENOMEM)) {
  85                         err = -ENOMEM;
  86                         break;
  87                 } else if (IS_ERR(dentry_page)) {
  88                         erofs_err(dir->i_sb,
  89                                   "fail to readdir of logical block %u of nid %llu",
  90                                   i, EROFS_I(dir)->nid);
  91                         err = -EFSCORRUPTED;
  92                         break;
  93                 }
  94
  95                 de = (struct erofs_dirent *)kmap(dentry_page);
  96
  97                 nameoff = le16_to_cpu(de->nameoff);
  98
  99                 if (nameoff < sizeof(struct erofs_dirent) ||
 100                     nameoff >= PAGE_SIZE) {
 101                         erofs_err(dir->i_sb,
 102                                   "invalid de[0].nameoff %u @ nid %llu",
 103                                   nameoff, EROFS_I(dir)->nid);
 104                         err = -EFSCORRUPTED;
 105                         goto skip_this;
 106                 }
 107
 108                 maxsize = min_t(unsigned int,
 109                                 dirsize - ctx->pos + ofs, PAGE_SIZE);
 110
 111                 /* search dirents at the arbitrary position */
 112                 if (initial) {
 113                         initial = false;
 114
 115                         ofs = roundup(ofs, sizeof(struct erofs_dirent));
 116                         if (ofs >= nameoff)
 117                                 goto skip_this;
 118                 }
 119
 120                 err = erofs_fill_dentries(dir, ctx, de, &ofs,
 121                                           nameoff, maxsize);
 122 skip_this:
 123                 kunmap(dentry_page);
 124
 125                 put_page(dentry_page);
 126
 127                 ctx->pos = blknr_to_addr(i) + ofs;
 128
 129                 if (err)
 130                         break;
 131                 ++i;
 132                 ofs = 0;
 133         }
 134         return err < 0 ? err : 0;
 135 }
 136
 137 const struct file_operations erofs_dir_fops = {
 138         .llseek         = generic_file_llseek,
 139         .read           = generic_read_dir,
 140         .iterate_shared = erofs_readdir,
 141 };
 142