fs/udf/dir.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * dir.c
   4  *
   5  * PURPOSE
   6  *  Directory handling routines for the OSTA-UDF(tm) filesystem.
   7  *
   8  * COPYRIGHT
   9  *  (C) 1998-2004 Ben Fennema
  10  *
  11  * HISTORY
  12  *
  13  *  10/05/98 dgb  Split directory operations into its own file
  14  *                Implemented directory reads via do_udf_readdir
  15  *  10/06/98      Made directory operations work!
  16  *  11/17/98      Rewrote directory to support ICBTAG_FLAG_AD_LONG
  17  *  11/25/98 blf  Rewrote directory handling (readdir+lookup) to support reading
  18  *                across blocks.
  19  *  12/12/98      Split out the lookup code to namei.c. bulk of directory
  20  *                code now in directory.c:udf_fileident_read.
  21  */
  22
  23 #include "udfdecl.h"
  24
  25 #include <linux/string.h>
  26 #include <linux/errno.h>
  27 #include <linux/mm.h>
  28 #include <linux/slab.h>
  29 #include <linux/bio.h>
  30 #include <linux/iversion.h>
  31
  32 #include "udf_i.h"
  33 #include "udf_sb.h"
  34
  35 static int udf_readdir(struct file *file, struct dir_context *ctx)
  36 {
  37         struct inode *dir = file_inode(file);
  38         loff_t nf_pos, emit_pos = 0;
  39         int flen;
  40         unsigned char *fname = NULL;
  41         int ret = 0;
  42         struct super_block *sb = dir->i_sb;
  43         bool pos_valid = false;
  44         struct udf_fileident_iter iter;
  45
  46         if (ctx->pos == 0) {
  47                 if (!dir_emit_dot(file, ctx))
  48                         return 0;
  49                 ctx->pos = 1;
  50         }
  51         nf_pos = (ctx->pos - 1) << 2;
  52         if (nf_pos >= dir->i_size)
  53                 goto out;
  54
  55         /*
  56          * Something changed since last readdir (either lseek was called or dir
  57          * changed)?  We need to verify the position correctly points at the
  58          * beginning of some dir entry so that the directory parsing code does
  59          * not get confused. Since UDF does not have any reliable way of
  60          * identifying beginning of dir entry (names are under user control),
  61          * we need to scan the directory from the beginning.
  62          */
  63         if (!inode_eq_iversion(dir, file->f_version)) {
  64                 emit_pos = nf_pos;
  65                 nf_pos = 0;
  66         } else {
  67                 pos_valid = true;
  68         }
  69
  70         fname = kmalloc(UDF_NAME_LEN, GFP_NOFS);
  71         if (!fname) {
  72                 ret = -ENOMEM;
  73                 goto out;
  74         }
  75
  76         for (ret = udf_fiiter_init(&iter, dir, nf_pos);
  77              !ret && iter.pos < dir->i_size;
  78              ret = udf_fiiter_advance(&iter)) {
  79                 struct kernel_lb_addr tloc;
  80                 udf_pblk_t iblock;
  81
  82                 /* Still not at offset where user asked us to read from? */
  83                 if (iter.pos < emit_pos)
  84                         continue;
  85
  86                 /* Update file position only if we got past the current one */
  87                 pos_valid = true;
  88                 ctx->pos = (iter.pos >> 2) + 1;
  89
  90                 if (iter.fi.fileCharacteristics & FID_FILE_CHAR_DELETED) {
  91                         if (!UDF_QUERY_FLAG(sb, UDF_FLAG_UNDELETE))
  92                                 continue;
  93                 }
  94
  95                 if (iter.fi.fileCharacteristics & FID_FILE_CHAR_HIDDEN) {
  96                         if (!UDF_QUERY_FLAG(sb, UDF_FLAG_UNHIDE))
  97                                 continue;
  98                 }
  99
 100                 if (iter.fi.fileCharacteristics & FID_FILE_CHAR_PARENT) {
 101                         if (!dir_emit_dotdot(file, ctx))
 102                                 goto out_iter;
 103                         continue;
 104                 }
 105
 106                 flen = udf_get_filename(sb, iter.name,
 107                                 iter.fi.lengthFileIdent, fname, UDF_NAME_LEN);
 108                 if (flen < 0)
 109                         continue;
 110
 111                 tloc = lelb_to_cpu(iter.fi.icb.extLocation);
 112                 iblock = udf_get_lb_pblock(sb, &tloc, 0);
 113                 if (!dir_emit(ctx, fname, flen, iblock, DT_UNKNOWN))
 114                         goto out_iter;
 115         }
 116
 117         if (!ret) {
 118                 ctx->pos = (iter.pos >> 2) + 1;
 119                 pos_valid = true;
 120         }
 121 out_iter:
 122         udf_fiiter_release(&iter);
 123 out:
 124         if (pos_valid)
 125                 file->f_version = inode_query_iversion(dir);
 126         kfree(fname);
 127
 128         return ret;
 129 }
 130
 131 /* readdir and lookup functions */
 132 const struct file_operations udf_dir_operations = {
 133         .llseek                 = generic_file_llseek,
 134         .read                   = generic_read_dir,
 135         .iterate_shared         = udf_readdir,
 136         .unlocked_ioctl         = udf_ioctl,
 137         .fsync                  = generic_file_fsync,
 138 };