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         bool shared = false;
  28         int res = -ENOTDIR;
  29         if (file->f_op->iterate_shared)
  30                 shared = true;
  31         else if (!file->f_op->iterate)
  32                 goto out;
  33
  34         res = security_file_permission(file, MAY_READ);
  35         if (res)
  36                 goto out;
  37
  38         if (shared) {
  39                 inode_lock_shared(inode);
  40         } else {
  41                 res = down_write_killable(&inode->i_rwsem);
  42                 if (res)
  43                         goto out;
  44         }
  45
  46         res = -ENOENT;
  47         if (!IS_DEADDIR(inode)) {
  48                 ctx->pos = file->f_pos;
  49                 if (shared)
  50                         res = file->f_op->iterate_shared(file, ctx);
  51                 else
  52                         res = file->f_op->iterate(file, ctx);
  53                 file->f_pos = ctx->pos;
  54                 fsnotify_access(file);
  55                 file_accessed(file);
  56         }
  57         if (shared)
  58                 inode_unlock_shared(inode);
  59         else
  60                 inode_unlock(inode);
  61 out:
  62         return res;
  63 }
  64 EXPORT_SYMBOL(iterate_dir);
  65
  66 /*
  67  * Traditional linux readdir() handling..
  68  *
  69  * "count=1" is a special case, meaning that the buffer is one
  70  * dirent-structure in size and that the code can't handle more
  71  * anyway. Thus the special "fillonedir()" function for that
  72  * case (the low-level handlers don't need to care about this).
  73  */
  74
  75 #ifdef __ARCH_WANT_OLD_READDIR
  76
  77 struct old_linux_dirent {
  78         unsigned long   d_ino;
  79         unsigned long   d_offset;
  80         unsigned short  d_namlen;
  81         char            d_name[1];
  82 };
  83
  84 struct readdir_callback {
  85         struct dir_context ctx;
  86         struct old_linux_dirent __user * dirent;
  87         int result;
  88 };
  89
  90 static int fillonedir(struct dir_context *ctx, const char *name, int namlen,
  91                       loff_t offset, u64 ino, unsigned int d_type)
  92 {
  93         struct readdir_callback *buf =
  94                 container_of(ctx, struct readdir_callback, ctx);
  95         struct old_linux_dirent __user * dirent;
  96         unsigned long d_ino;
  97
  98         if (buf->result)
  99                 return -EINVAL;
 100         d_ino = ino;
 101         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 102                 buf->result = -EOVERFLOW;
 103                 return -EOVERFLOW;
 104         }
 105         buf->result++;
 106         dirent = buf->dirent;
 107         if (!access_ok(VERIFY_WRITE, dirent,
 108                         (unsigned long)(dirent->d_name + namlen + 1) -
 109                                 (unsigned long)dirent))
 110                 goto efault;
 111         if (    __put_user(d_ino, &dirent->d_ino) ||
 112                 __put_user(offset, &dirent->d_offset) ||
 113                 __put_user(namlen, &dirent->d_namlen) ||
 114                 __copy_to_user(dirent->d_name, name, namlen) ||
 115                 __put_user(0, dirent->d_name + namlen))
 116                 goto efault;
 117         return 0;
 118 efault:
 119         buf->result = -EFAULT;
 120         return -EFAULT;
 121 }
 122
 123 SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
 124                 struct old_linux_dirent __user *, dirent, unsigned int, count)
 125 {
 126         int error;
 127         struct fd f = fdget_pos(fd);
 128         struct readdir_callback buf = {
 129                 .ctx.actor = fillonedir,
 130                 .dirent = dirent
 131         };
 132
 133         if (!f.file)
 134                 return -EBADF;
 135
 136         error = iterate_dir(f.file, &buf.ctx);
 137         if (buf.result)
 138                 error = buf.result;
 139
 140         fdput_pos(f);
 141         return error;
 142 }
 143
 144 #endif /* __ARCH_WANT_OLD_READDIR */
 145
 146 /*
 147  * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 148  * interface.
 149  */
 150 struct linux_dirent {
 151         unsigned long   d_ino;
 152         unsigned long   d_off;
 153         unsigned short  d_reclen;
 154         char            d_name[1];
 155 };
 156
 157 struct getdents_callback {
 158         struct dir_context ctx;
 159         struct linux_dirent __user * current_dir;
 160         struct linux_dirent __user * previous;
 161         int count;
 162         int error;
 163 };
 164
 165 static int filldir(struct dir_context *ctx, const char *name, int namlen,
 166                    loff_t offset, u64 ino, unsigned int d_type)
 167 {
 168         struct linux_dirent __user * dirent;
 169         struct getdents_callback *buf =
 170                 container_of(ctx, struct getdents_callback, ctx);
 171         unsigned long d_ino;
 172         int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
 173                 sizeof(long));
 174
 175         buf->error = -EINVAL;   /* only used if we fail.. */
 176         if (reclen > buf->count)
 177                 return -EINVAL;
 178         d_ino = ino;
 179         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 180                 buf->error = -EOVERFLOW;
 181                 return -EOVERFLOW;
 182         }
 183         dirent = buf->previous;
 184         if (dirent) {
 185                 if (signal_pending(current))
 186                         return -EINTR;
 187                 if (__put_user(offset, &dirent->d_off))
 188                         goto efault;
 189         }
 190         dirent = buf->current_dir;
 191         if (__put_user(d_ino, &dirent->d_ino))
 192                 goto efault;
 193         if (__put_user(reclen, &dirent->d_reclen))
 194                 goto efault;
 195         if (copy_to_user(dirent->d_name, name, namlen))
 196                 goto efault;
 197         if (__put_user(0, dirent->d_name + namlen))
 198                 goto efault;
 199         if (__put_user(d_type, (char __user *) dirent + reclen - 1))
 200                 goto efault;
 201         buf->previous = dirent;
 202         dirent = (void __user *)dirent + reclen;
 203         buf->current_dir = dirent;
 204         buf->count -= reclen;
 205         return 0;
 206 efault:
 207         buf->error = -EFAULT;
 208         return -EFAULT;
 209 }
 210
 211 SYSCALL_DEFINE3(getdents, unsigned int, fd,
 212                 struct linux_dirent __user *, dirent, unsigned int, count)
 213 {
 214         struct fd f;
 215         struct linux_dirent __user * lastdirent;
 216         struct getdents_callback buf = {
 217                 .ctx.actor = filldir,
 218                 .count = count,
 219                 .current_dir = dirent
 220         };
 221         int error;
 222
 223         if (!access_ok(VERIFY_WRITE, dirent, count))
 224                 return -EFAULT;
 225
 226         f = fdget_pos(fd);
 227         if (!f.file)
 228                 return -EBADF;
 229
 230         error = iterate_dir(f.file, &buf.ctx);
 231         if (error >= 0)
 232                 error = buf.error;
 233         lastdirent = buf.previous;
 234         if (lastdirent) {
 235                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 236                         error = -EFAULT;
 237                 else
 238                         error = count - buf.count;
 239         }
 240         fdput_pos(f);
 241         return error;
 242 }
 243
 244 struct getdents_callback64 {
 245         struct dir_context ctx;
 246         struct linux_dirent64 __user * current_dir;
 247         struct linux_dirent64 __user * previous;
 248         int count;
 249         int error;
 250 };
 251
 252 static int filldir64(struct dir_context *ctx, const char *name, int namlen,
 253                      loff_t offset, u64 ino, unsigned int d_type)
 254 {
 255         struct linux_dirent64 __user *dirent;
 256         struct getdents_callback64 *buf =
 257                 container_of(ctx, struct getdents_callback64, ctx);
 258         int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 259                 sizeof(u64));
 260
 261         buf->error = -EINVAL;   /* only used if we fail.. */
 262         if (reclen > buf->count)
 263                 return -EINVAL;
 264         dirent = buf->previous;
 265         if (dirent) {
 266                 if (signal_pending(current))
 267                         return -EINTR;
 268                 if (__put_user(offset, &dirent->d_off))
 269                         goto efault;
 270         }
 271         dirent = buf->current_dir;
 272         if (__put_user(ino, &dirent->d_ino))
 273                 goto efault;
 274         if (__put_user(0, &dirent->d_off))
 275                 goto efault;
 276         if (__put_user(reclen, &dirent->d_reclen))
 277                 goto efault;
 278         if (__put_user(d_type, &dirent->d_type))
 279                 goto efault;
 280         if (copy_to_user(dirent->d_name, name, namlen))
 281                 goto efault;
 282         if (__put_user(0, dirent->d_name + namlen))
 283                 goto efault;
 284         buf->previous = dirent;
 285         dirent = (void __user *)dirent + reclen;
 286         buf->current_dir = dirent;
 287         buf->count -= reclen;
 288         return 0;
 289 efault:
 290         buf->error = -EFAULT;
 291         return -EFAULT;
 292 }
 293
 294 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 295                 struct linux_dirent64 __user *, dirent, unsigned int, count)
 296 {
 297         struct fd f;
 298         struct linux_dirent64 __user * lastdirent;
 299         struct getdents_callback64 buf = {
 300                 .ctx.actor = filldir64,
 301                 .count = count,
 302                 .current_dir = dirent
 303         };
 304         int error;
 305
 306         if (!access_ok(VERIFY_WRITE, dirent, count))
 307                 return -EFAULT;
 308
 309         f = fdget_pos(fd);
 310         if (!f.file)
 311                 return -EBADF;
 312
 313         error = iterate_dir(f.file, &buf.ctx);
 314         if (error >= 0)
 315                 error = buf.error;
 316         lastdirent = buf.previous;
 317         if (lastdirent) {
 318                 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
 319                 if (__put_user(d_off, &lastdirent->d_off))
 320                         error = -EFAULT;
 321                 else
 322                         error = count - buf.count;
 323         }
 324         fdput_pos(f);
 325         return error;
 326 }