fs/readdir.c

   1 /*
   2  *  linux/fs/readdir.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  */
   6
   7 #include <linux/stddef.h>
   8 #include <linux/kernel.h>
   9 #include <linux/export.h>
  10 #include <linux/time.h>
  11 #include <linux/mm.h>
  12 #include <linux/errno.h>
  13 #include <linux/stat.h>
  14 #include <linux/file.h>
  15 #include <linux/fs.h>
  16 #include <linux/dirent.h>
  17 #include <linux/security.h>
  18 #include <linux/syscalls.h>
  19 #include <linux/unistd.h>
  20
  21 #include <asm/uaccess.h>
  22
  23 int iterate_dir(struct file *file, struct dir_context *ctx)
  24 {
  25         struct inode *inode = file_inode(file);
  26         int res = -ENOTDIR;
  27         if (!file->f_op || !file->f_op->iterate)
  28                 goto out;
  29
  30         res = security_file_permission(file, MAY_READ);
  31         if (res)
  32                 goto out;
  33
  34         res = mutex_lock_killable(&inode->i_mutex);
  35         if (res)
  36                 goto out;
  37
  38         res = -ENOENT;
  39         if (!IS_DEADDIR(inode)) {
  40                 ctx->pos = file->f_pos;
  41                 res = file->f_op->iterate(file, ctx);
  42                 file->f_pos = ctx->pos;
  43                 file_accessed(file);
  44         }
  45         mutex_unlock(&inode->i_mutex);
  46 out:
  47         return res;
  48 }
  49 EXPORT_SYMBOL(iterate_dir);
  50
  51 /*
  52  * Traditional linux readdir() handling..
  53  *
  54  * "count=1" is a special case, meaning that the buffer is one
  55  * dirent-structure in size and that the code can't handle more
  56  * anyway. Thus the special "fillonedir()" function for that
  57  * case (the low-level handlers don't need to care about this).
  58  */
  59
  60 #ifdef __ARCH_WANT_OLD_READDIR
  61
  62 struct old_linux_dirent {
  63         unsigned long   d_ino;
  64         unsigned long   d_offset;
  65         unsigned short  d_namlen;
  66         char            d_name[1];
  67 };
  68
  69 struct readdir_callback {
  70         struct dir_context ctx;
  71         struct old_linux_dirent __user * dirent;
  72         int result;
  73 };
  74
  75 static int fillonedir(void * __buf, const char * name, int namlen, loff_t offset,
  76                       u64 ino, unsigned int d_type)
  77 {
  78         struct readdir_callback *buf = (struct readdir_callback *) __buf;
  79         struct old_linux_dirent __user * dirent;
  80         unsigned long d_ino;
  81
  82         if (buf->result)
  83                 return -EINVAL;
  84         d_ino = ino;
  85         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
  86                 buf->result = -EOVERFLOW;
  87                 return -EOVERFLOW;
  88         }
  89         buf->result++;
  90         dirent = buf->dirent;
  91         if (!access_ok(VERIFY_WRITE, dirent,
  92                         (unsigned long)(dirent->d_name + namlen + 1) -
  93                                 (unsigned long)dirent))
  94                 goto efault;
  95         if (    __put_user(d_ino, &dirent->d_ino) ||
  96                 __put_user(offset, &dirent->d_offset) ||
  97                 __put_user(namlen, &dirent->d_namlen) ||
  98                 __copy_to_user(dirent->d_name, name, namlen) ||
  99                 __put_user(0, dirent->d_name + namlen))
 100                 goto efault;
 101         return 0;
 102 efault:
 103         buf->result = -EFAULT;
 104         return -EFAULT;
 105 }
 106
 107 SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
 108                 struct old_linux_dirent __user *, dirent, unsigned int, count)
 109 {
 110         int error;
 111         struct fd f = fdget(fd);
 112         struct readdir_callback buf = {
 113                 .ctx.actor = fillonedir,
 114                 .dirent = dirent
 115         };
 116
 117         if (!f.file)
 118                 return -EBADF;
 119
 120         error = iterate_dir(f.file, &buf.ctx);
 121         if (buf.result)
 122                 error = buf.result;
 123
 124         fdput(f);
 125         return error;
 126 }
 127
 128 #endif /* __ARCH_WANT_OLD_READDIR */
 129
 130 /*
 131  * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 132  * interface.
 133  */
 134 struct linux_dirent {
 135         unsigned long   d_ino;
 136         unsigned long   d_off;
 137         unsigned short  d_reclen;
 138         char            d_name[1];
 139 };
 140
 141 struct getdents_callback {
 142         struct dir_context ctx;
 143         struct linux_dirent __user * current_dir;
 144         struct linux_dirent __user * previous;
 145         int count;
 146         int error;
 147 };
 148
 149 static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
 150                    u64 ino, unsigned int d_type)
 151 {
 152         struct linux_dirent __user * dirent;
 153         struct getdents_callback * buf = (struct getdents_callback *) __buf;
 154         unsigned long d_ino;
 155         int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
 156                 sizeof(long));
 157
 158         buf->error = -EINVAL;   /* only used if we fail.. */
 159         if (reclen > buf->count)
 160                 return -EINVAL;
 161         d_ino = ino;
 162         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 163                 buf->error = -EOVERFLOW;
 164                 return -EOVERFLOW;
 165         }
 166         dirent = buf->previous;
 167         if (dirent) {
 168                 if (__put_user(offset, &dirent->d_off))
 169                         goto efault;
 170         }
 171         dirent = buf->current_dir;
 172         if (__put_user(d_ino, &dirent->d_ino))
 173                 goto efault;
 174         if (__put_user(reclen, &dirent->d_reclen))
 175                 goto efault;
 176         if (copy_to_user(dirent->d_name, name, namlen))
 177                 goto efault;
 178         if (__put_user(0, dirent->d_name + namlen))
 179                 goto efault;
 180         if (__put_user(d_type, (char __user *) dirent + reclen - 1))
 181                 goto efault;
 182         buf->previous = dirent;
 183         dirent = (void __user *)dirent + reclen;
 184         buf->current_dir = dirent;
 185         buf->count -= reclen;
 186         return 0;
 187 efault:
 188         buf->error = -EFAULT;
 189         return -EFAULT;
 190 }
 191
 192 SYSCALL_DEFINE3(getdents, unsigned int, fd,
 193                 struct linux_dirent __user *, dirent, unsigned int, count)
 194 {
 195         struct fd f;
 196         struct linux_dirent __user * lastdirent;
 197         struct getdents_callback buf = {
 198                 .ctx.actor = filldir,
 199                 .count = count,
 200                 .current_dir = dirent
 201         };
 202         int error;
 203
 204         if (!access_ok(VERIFY_WRITE, dirent, count))
 205                 return -EFAULT;
 206
 207         f = fdget(fd);
 208         if (!f.file)
 209                 return -EBADF;
 210
 211         error = iterate_dir(f.file, &buf.ctx);
 212         if (error >= 0)
 213                 error = buf.error;
 214         lastdirent = buf.previous;
 215         if (lastdirent) {
 216                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 217                         error = -EFAULT;
 218                 else
 219                         error = count - buf.count;
 220         }
 221         fdput(f);
 222         return error;
 223 }
 224
 225 struct getdents_callback64 {
 226         struct dir_context ctx;
 227         struct linux_dirent64 __user * current_dir;
 228         struct linux_dirent64 __user * previous;
 229         int count;
 230         int error;
 231 };
 232
 233 static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
 234                      u64 ino, unsigned int d_type)
 235 {
 236         struct linux_dirent64 __user *dirent;
 237         struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
 238         int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 239                 sizeof(u64));
 240
 241         buf->error = -EINVAL;   /* only used if we fail.. */
 242         if (reclen > buf->count)
 243                 return -EINVAL;
 244         dirent = buf->previous;
 245         if (dirent) {
 246                 if (__put_user(offset, &dirent->d_off))
 247                         goto efault;
 248         }
 249         dirent = buf->current_dir;
 250         if (__put_user(ino, &dirent->d_ino))
 251                 goto efault;
 252         if (__put_user(0, &dirent->d_off))
 253                 goto efault;
 254         if (__put_user(reclen, &dirent->d_reclen))
 255                 goto efault;
 256         if (__put_user(d_type, &dirent->d_type))
 257                 goto efault;
 258         if (copy_to_user(dirent->d_name, name, namlen))
 259                 goto efault;
 260         if (__put_user(0, dirent->d_name + namlen))
 261                 goto efault;
 262         buf->previous = dirent;
 263         dirent = (void __user *)dirent + reclen;
 264         buf->current_dir = dirent;
 265         buf->count -= reclen;
 266         return 0;
 267 efault:
 268         buf->error = -EFAULT;
 269         return -EFAULT;
 270 }
 271
 272 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 273                 struct linux_dirent64 __user *, dirent, unsigned int, count)
 274 {
 275         struct fd f;
 276         struct linux_dirent64 __user * lastdirent;
 277         struct getdents_callback64 buf = {
 278                 .ctx.actor = filldir64,
 279                 .count = count,
 280                 .current_dir = dirent
 281         };
 282         int error;
 283
 284         if (!access_ok(VERIFY_WRITE, dirent, count))
 285                 return -EFAULT;
 286
 287         f = fdget(fd);
 288         if (!f.file)
 289                 return -EBADF;
 290
 291         error = iterate_dir(f.file, &buf.ctx);
 292         if (error >= 0)
 293                 error = buf.error;
 294         lastdirent = buf.previous;
 295         if (lastdirent) {
 296                 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
 297                 if (__put_user(d_off, &lastdirent->d_off))
 298                         error = -EFAULT;
 299                 else
 300                         error = count - buf.count;
 301         }
 302         fdput(f);
 303         return error;
 304 }