drivers/staging/erofs/dir.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/drivers/staging/erofs/dir.c
   4  *
   5  * Copyright (C) 2017-2018 HUAWEI, Inc.
   6  *             http://www.huawei.com/
   7  * Created by Gao Xiang <gaoxiang25@huawei.com>
   8  */
   9 #include "internal.h"
  10
  11 static void debug_one_dentry(unsigned char d_type, const char *de_name,
  12                              unsigned int de_namelen)
  13 {
  14 #ifdef CONFIG_EROFS_FS_DEBUG
  15         /* since the on-disk name could not have the trailing '\0' */
  16         unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
  17
  18         memcpy(dbg_namebuf, de_name, de_namelen);
  19         dbg_namebuf[de_namelen] = '\0';
  20
  21         debugln("found dirent %s de_len %u d_type %d", dbg_namebuf,
  22                 de_namelen, d_type);
  23 #endif
  24 }
  25
  26 static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
  27                                void *dentry_blk, unsigned int *ofs,
  28                                unsigned int nameoff, unsigned int maxsize)
  29 {
  30         struct erofs_dirent *de = dentry_blk + *ofs;
  31         const struct erofs_dirent *end = dentry_blk + nameoff;
  32
  33         while (de < end) {
  34                 const char *de_name;
  35                 unsigned int de_namelen;
  36                 unsigned char d_type;
  37
  38                 d_type = fs_ftype_to_dtype(de->file_type);
  39
  40                 nameoff = le16_to_cpu(de->nameoff);
  41                 de_name = (char *)dentry_blk + nameoff;
  42
  43                 /* the last dirent in the block? */
  44                 if (de + 1 >= end)
  45                         de_namelen = strnlen(de_name, maxsize - nameoff);
  46                 else
  47                         de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
  48
  49                 /* a corrupted entry is found */
  50                 if (unlikely(nameoff + de_namelen > maxsize ||
  51                              de_namelen > EROFS_NAME_LEN)) {
  52                         errln("bogus dirent @ nid %llu", EROFS_V(dir)->nid);
  53                         DBG_BUGON(1);
  54                         return -EFSCORRUPTED;
  55                 }
  56
  57                 debug_one_dentry(d_type, de_name, de_namelen);
  58                 if (!dir_emit(ctx, de_name, de_namelen,
  59                               le64_to_cpu(de->nid), d_type))
  60                         /* stopped by some reason */
  61                         return 1;
  62                 ++de;
  63                 *ofs += sizeof(struct erofs_dirent);
  64         }
  65         *ofs = maxsize;
  66         return 0;
  67 }
  68
  69 static int erofs_readdir(struct file *f, struct dir_context *ctx)
  70 {
  71         struct inode *dir = file_inode(f);
  72         struct address_space *mapping = dir->i_mapping;
  73         const size_t dirsize = i_size_read(dir);
  74         unsigned int i = ctx->pos / EROFS_BLKSIZ;
  75         unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
  76         int err = 0;
  77         bool initial = true;
  78
  79         while (ctx->pos < dirsize) {
  80                 struct page *dentry_page;
  81                 struct erofs_dirent *de;
  82                 unsigned int nameoff, maxsize;
  83
  84                 dentry_page = read_mapping_page(mapping, i, NULL);
  85                 if (dentry_page == ERR_PTR(-ENOMEM)) {
  86                         err = -ENOMEM;
  87                         break;
  88                 } else if (IS_ERR(dentry_page)) {
  89                         errln("fail to readdir of logical block %u of nid %llu",
  90                               i, EROFS_V(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 (unlikely(nameoff < sizeof(struct erofs_dirent) ||
 100                              nameoff >= PAGE_SIZE)) {
 101                         errln("%s, invalid de[0].nameoff %u @ nid %llu",
 102                               __func__, nameoff, EROFS_V(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 (unlikely(initial)) {
 112                         initial = false;
 113
 114                         ofs = roundup(ofs, sizeof(struct erofs_dirent));
 115                         if (unlikely(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 (unlikely(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 };
 141