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/fsnotify.h>
  17 #include <linux/dirent.h>
  18 #include <linux/security.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/unistd.h>
  21
  22 #include <asm/uaccess.h>
  23
  24 int iterate_dir(struct file *file, struct dir_context *ctx)
  25 {
  26         struct inode *inode = file_inode(file);
  27         int res = -ENOTDIR;
  28         if (!file->f_op->iterate)
  29                 goto out;
  30
  31         res = security_file_permission(file, MAY_READ);
  32         if (res)
  33                 goto out;
  34
  35         res = mutex_lock_killable(&inode->i_mutex);
  36         if (res)
  37                 goto out;
  38
  39         res = -ENOENT;
  40         if (!IS_DEADDIR(inode)) {
  41                 ctx->pos = file->f_pos;
  42                 res = file->f_op->iterate(file, ctx);
  43                 file->f_pos = ctx->pos;
  44                 fsnotify_access(file);
  45                 file_accessed(file);
  46         }
  47         mutex_unlock(&inode->i_mutex);
  48 out:
  49         return res;
  50 }
  51 EXPORT_SYMBOL(iterate_dir);
  52
  53 /*
  54  * Traditional linux readdir() handling..
  55  *
  56  * "count=1" is a special case, meaning that the buffer is one
  57  * dirent-structure in size and that the code can't handle more
  58  * anyway. Thus the special "fillonedir()" function for that
  59  * case (the low-level handlers don't need to care about this).
  60  */
  61
  62 #ifdef __ARCH_WANT_OLD_READDIR
  63
  64 struct old_linux_dirent {
  65         unsigned long   d_ino;
  66         unsigned long   d_offset;
  67         unsigned short  d_namlen;
  68         char            d_name[1];
  69 };
  70
  71 struct readdir_callback {
  72         struct dir_context ctx;
  73         struct old_linux_dirent __user * dirent;
  74         int result;
  75 };
  76
  77 static int fillonedir(void * __buf, const char * name, int namlen, loff_t offset,
  78                       u64 ino, unsigned int d_type)
  79 {
  80         struct readdir_callback *buf = (struct readdir_callback *) __buf;
  81         struct old_linux_dirent __user * dirent;
  82         unsigned long d_ino;
  83
  84         if (buf->result)
  85                 return -EINVAL;
  86         d_ino = ino;
  87         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
  88                 buf->result = -EOVERFLOW;
  89                 return -EOVERFLOW;
  90         }
  91         buf->result++;
  92         dirent = buf->dirent;
  93         if (!access_ok(VERIFY_WRITE, dirent,
  94                         (unsigned long)(dirent->d_name + namlen + 1) -
  95                                 (unsigned long)dirent))
  96                 goto efault;
  97         if (    __put_user(d_ino, &dirent->d_ino) ||
  98                 __put_user(offset, &dirent->d_offset) ||
  99                 __put_user(namlen, &dirent->d_namlen) ||
 100                 __copy_to_user(dirent->d_name, name, namlen) ||
 101                 __put_user(0, dirent->d_name + namlen))
 102                 goto efault;
 103         return 0;
 104 efault:
 105         buf->result = -EFAULT;
 106         return -EFAULT;
 107 }
 108
 109 SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
 110                 struct old_linux_dirent __user *, dirent, unsigned int, count)
 111 {
 112         int error;
 113         struct fd f = fdget(fd);
 114         struct readdir_callback buf = {
 115                 .ctx.actor = fillonedir,
 116                 .dirent = dirent
 117         };
 118
 119         if (!f.file)
 120                 return -EBADF;
 121
 122         error = iterate_dir(f.file, &buf.ctx);
 123         if (buf.result)
 124                 error = buf.result;
 125
 126         fdput(f);
 127         return error;
 128 }
 129
 130 #endif /* __ARCH_WANT_OLD_READDIR */
 131
 132 /*
 133  * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 134  * interface.
 135  */
 136 struct linux_dirent {
 137         unsigned long   d_ino;
 138         unsigned long   d_off;
 139         unsigned short  d_reclen;
 140         char            d_name[1];
 141 };
 142
 143 struct getdents_callback {
 144         struct dir_context ctx;
 145         struct linux_dirent __user * current_dir;
 146         struct linux_dirent __user * previous;
 147         int count;
 148         int error;
 149 };
 150
 151 static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
 152                    u64 ino, unsigned int d_type)
 153 {
 154         struct linux_dirent __user * dirent;
 155         struct getdents_callback * buf = (struct getdents_callback *) __buf;
 156         unsigned long d_ino;
 157         int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
 158                 sizeof(long));
 159
 160         buf->error = -EINVAL;   /* only used if we fail.. */
 161         if (reclen > buf->count)
 162                 return -EINVAL;
 163         d_ino = ino;
 164         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 165                 buf->error = -EOVERFLOW;
 166                 return -EOVERFLOW;
 167         }
 168         dirent = buf->previous;
 169         if (dirent) {
 170                 if (__put_user(offset, &dirent->d_off))
 171                         goto efault;
 172         }
 173         dirent = buf->current_dir;
 174         if (__put_user(d_ino, &dirent->d_ino))
 175                 goto efault;
 176         if (__put_user(reclen, &dirent->d_reclen))
 177                 goto efault;
 178         if (copy_to_user(dirent->d_name, name, namlen))
 179                 goto efault;
 180         if (__put_user(0, dirent->d_name + namlen))
 181                 goto efault;
 182         if (__put_user(d_type, (char __user *) dirent + reclen - 1))
 183                 goto efault;
 184         buf->previous = dirent;
 185         dirent = (void __user *)dirent + reclen;
 186         buf->current_dir = dirent;
 187         buf->count -= reclen;
 188         return 0;
 189 efault:
 190         buf->error = -EFAULT;
 191         return -EFAULT;
 192 }
 193
 194 SYSCALL_DEFINE3(getdents, unsigned int, fd,
 195                 struct linux_dirent __user *, dirent, unsigned int, count)
 196 {
 197         struct fd f;
 198         struct linux_dirent __user * lastdirent;
 199         struct getdents_callback buf = {
 200                 .ctx.actor = filldir,
 201                 .count = count,
 202                 .current_dir = dirent
 203         };
 204         int error;
 205
 206         if (!access_ok(VERIFY_WRITE, dirent, count))
 207                 return -EFAULT;
 208
 209         f = fdget(fd);
 210         if (!f.file)
 211                 return -EBADF;
 212
 213         error = iterate_dir(f.file, &buf.ctx);
 214         if (error >= 0)
 215                 error = buf.error;
 216         lastdirent = buf.previous;
 217         if (lastdirent) {
 218                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 219                         error = -EFAULT;
 220                 else
 221                         error = count - buf.count;
 222         }
 223         fdput(f);
 224         return error;
 225 }
 226
 227 struct getdents_callback64 {
 228         struct dir_context ctx;
 229         struct linux_dirent64 __user * current_dir;
 230         struct linux_dirent64 __user * previous;
 231         int count;
 232         int error;
 233 };
 234
 235 static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
 236                      u64 ino, unsigned int d_type)
 237 {
 238         struct linux_dirent64 __user *dirent;
 239         struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
 240         int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 241                 sizeof(u64));
 242
 243         buf->error = -EINVAL;   /* only used if we fail.. */
 244         if (reclen > buf->count)
 245                 return -EINVAL;
 246         dirent = buf->previous;
 247         if (dirent) {
 248                 if (__put_user(offset, &dirent->d_off))
 249                         goto efault;
 250         }
 251         dirent = buf->current_dir;
 252         if (__put_user(ino, &dirent->d_ino))
 253                 goto efault;
 254         if (__put_user(0, &dirent->d_off))
 255                 goto efault;
 256         if (__put_user(reclen, &dirent->d_reclen))
 257                 goto efault;
 258         if (__put_user(d_type, &dirent->d_type))
 259                 goto efault;
 260         if (copy_to_user(dirent->d_name, name, namlen))
 261                 goto efault;
 262         if (__put_user(0, dirent->d_name + namlen))
 263                 goto efault;
 264         buf->previous = dirent;
 265         dirent = (void __user *)dirent + reclen;
 266         buf->current_dir = dirent;
 267         buf->count -= reclen;
 268         return 0;
 269 efault:
 270         buf->error = -EFAULT;
 271         return -EFAULT;
 272 }
 273
 274 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 275                 struct linux_dirent64 __user *, dirent, unsigned int, count)
 276 {
 277         struct fd f;
 278         struct linux_dirent64 __user * lastdirent;
 279         struct getdents_callback64 buf = {
 280                 .ctx.actor = filldir64,
 281                 .count = count,
 282                 .current_dir = dirent
 283         };
 284         int error;
 285
 286         if (!access_ok(VERIFY_WRITE, dirent, count))
 287                 return -EFAULT;
 288
 289         f = fdget(fd);
 290         if (!f.file)
 291                 return -EBADF;
 292
 293         error = iterate_dir(f.file, &buf.ctx);
 294         if (error >= 0)
 295                 error = buf.error;
 296         lastdirent = buf.previous;
 297         if (lastdirent) {
 298                 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
 299                 if (__put_user(d_off, &lastdirent->d_off))
 300                         error = -EFAULT;
 301                 else
 302                         error = count - buf.count;
 303         }
 304         fdput(f);
 305         return error;
 306 }