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(struct dir_context *ctx, const char *name, int namlen,
  78                       loff_t offset, u64 ino, unsigned int d_type)
  79 {
  80         struct readdir_callback *buf =
  81                 container_of(ctx, struct readdir_callback, ctx);
  82         struct old_linux_dirent __user * dirent;
  83         unsigned long d_ino;
  84
  85         if (buf->result)
  86                 return -EINVAL;
  87         d_ino = ino;
  88         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
  89                 buf->result = -EOVERFLOW;
  90                 return -EOVERFLOW;
  91         }
  92         buf->result++;
  93         dirent = buf->dirent;
  94         if (!access_ok(VERIFY_WRITE, dirent,
  95                         (unsigned long)(dirent->d_name + namlen + 1) -
  96                                 (unsigned long)dirent))
  97                 goto efault;
  98         if (    __put_user(d_ino, &dirent->d_ino) ||
  99                 __put_user(offset, &dirent->d_offset) ||
 100                 __put_user(namlen, &dirent->d_namlen) ||
 101                 __copy_to_user(dirent->d_name, name, namlen) ||
 102                 __put_user(0, dirent->d_name + namlen))
 103                 goto efault;
 104         return 0;
 105 efault:
 106         buf->result = -EFAULT;
 107         return -EFAULT;
 108 }
 109
 110 SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
 111                 struct old_linux_dirent __user *, dirent, unsigned int, count)
 112 {
 113         int error;
 114         struct fd f = fdget(fd);
 115         struct readdir_callback buf = {
 116                 .ctx.actor = fillonedir,
 117                 .dirent = dirent
 118         };
 119
 120         if (!f.file)
 121                 return -EBADF;
 122
 123         error = iterate_dir(f.file, &buf.ctx);
 124         if (buf.result)
 125                 error = buf.result;
 126
 127         fdput(f);
 128         return error;
 129 }
 130
 131 #endif /* __ARCH_WANT_OLD_READDIR */
 132
 133 /*
 134  * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 135  * interface.
 136  */
 137 struct linux_dirent {
 138         unsigned long   d_ino;
 139         unsigned long   d_off;
 140         unsigned short  d_reclen;
 141         char            d_name[1];
 142 };
 143
 144 struct getdents_callback {
 145         struct dir_context ctx;
 146         struct linux_dirent __user * current_dir;
 147         struct linux_dirent __user * previous;
 148         int count;
 149         int error;
 150 };
 151
 152 static int filldir(struct dir_context *ctx, const char *name, int namlen,
 153                    loff_t offset, u64 ino, unsigned int d_type)
 154 {
 155         struct linux_dirent __user * dirent;
 156         struct getdents_callback *buf =
 157                 container_of(ctx, struct getdents_callback, ctx);
 158         unsigned long d_ino;
 159         int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
 160                 sizeof(long));
 161
 162         buf->error = -EINVAL;   /* only used if we fail.. */
 163         if (reclen > buf->count)
 164                 return -EINVAL;
 165         d_ino = ino;
 166         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 167                 buf->error = -EOVERFLOW;
 168                 return -EOVERFLOW;
 169         }
 170         dirent = buf->previous;
 171         if (dirent) {
 172                 if (__put_user(offset, &dirent->d_off))
 173                         goto efault;
 174         }
 175         dirent = buf->current_dir;
 176         if (__put_user(d_ino, &dirent->d_ino))
 177                 goto efault;
 178         if (__put_user(reclen, &dirent->d_reclen))
 179                 goto efault;
 180         if (copy_to_user(dirent->d_name, name, namlen))
 181                 goto efault;
 182         if (__put_user(0, dirent->d_name + namlen))
 183                 goto efault;
 184         if (__put_user(d_type, (char __user *) dirent + reclen - 1))
 185                 goto efault;
 186         buf->previous = dirent;
 187         dirent = (void __user *)dirent + reclen;
 188         buf->current_dir = dirent;
 189         buf->count -= reclen;
 190         return 0;
 191 efault:
 192         buf->error = -EFAULT;
 193         return -EFAULT;
 194 }
 195
 196 SYSCALL_DEFINE3(getdents, unsigned int, fd,
 197                 struct linux_dirent __user *, dirent, unsigned int, count)
 198 {
 199         struct fd f;
 200         struct linux_dirent __user * lastdirent;
 201         struct getdents_callback buf = {
 202                 .ctx.actor = filldir,
 203                 .count = count,
 204                 .current_dir = dirent
 205         };
 206         int error;
 207
 208         if (!access_ok(VERIFY_WRITE, dirent, count))
 209                 return -EFAULT;
 210
 211         f = fdget(fd);
 212         if (!f.file)
 213                 return -EBADF;
 214
 215         error = iterate_dir(f.file, &buf.ctx);
 216         if (error >= 0)
 217                 error = buf.error;
 218         lastdirent = buf.previous;
 219         if (lastdirent) {
 220                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 221                         error = -EFAULT;
 222                 else
 223                         error = count - buf.count;
 224         }
 225         fdput(f);
 226         return error;
 227 }
 228
 229 struct getdents_callback64 {
 230         struct dir_context ctx;
 231         struct linux_dirent64 __user * current_dir;
 232         struct linux_dirent64 __user * previous;
 233         int count;
 234         int error;
 235 };
 236
 237 static int filldir64(struct dir_context *ctx, const char *name, int namlen,
 238                      loff_t offset, u64 ino, unsigned int d_type)
 239 {
 240         struct linux_dirent64 __user *dirent;
 241         struct getdents_callback64 *buf =
 242                 container_of(ctx, struct getdents_callback64, ctx);
 243         int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 244                 sizeof(u64));
 245
 246         buf->error = -EINVAL;   /* only used if we fail.. */
 247         if (reclen > buf->count)
 248                 return -EINVAL;
 249         dirent = buf->previous;
 250         if (dirent) {
 251                 if (__put_user(offset, &dirent->d_off))
 252                         goto efault;
 253         }
 254         dirent = buf->current_dir;
 255         if (__put_user(ino, &dirent->d_ino))
 256                 goto efault;
 257         if (__put_user(0, &dirent->d_off))
 258                 goto efault;
 259         if (__put_user(reclen, &dirent->d_reclen))
 260                 goto efault;
 261         if (__put_user(d_type, &dirent->d_type))
 262                 goto efault;
 263         if (copy_to_user(dirent->d_name, name, namlen))
 264                 goto efault;
 265         if (__put_user(0, dirent->d_name + namlen))
 266                 goto efault;
 267         buf->previous = dirent;
 268         dirent = (void __user *)dirent + reclen;
 269         buf->current_dir = dirent;
 270         buf->count -= reclen;
 271         return 0;
 272 efault:
 273         buf->error = -EFAULT;
 274         return -EFAULT;
 275 }
 276
 277 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 278                 struct linux_dirent64 __user *, dirent, unsigned int, count)
 279 {
 280         struct fd f;
 281         struct linux_dirent64 __user * lastdirent;
 282         struct getdents_callback64 buf = {
 283                 .ctx.actor = filldir64,
 284                 .count = count,
 285                 .current_dir = dirent
 286         };
 287         int error;
 288
 289         if (!access_ok(VERIFY_WRITE, dirent, count))
 290                 return -EFAULT;
 291
 292         f = fdget(fd);
 293         if (!f.file)
 294                 return -EBADF;
 295
 296         error = iterate_dir(f.file, &buf.ctx);
 297         if (error >= 0)
 298                 error = buf.error;
 299         lastdirent = buf.previous;
 300         if (lastdirent) {
 301                 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
 302                 if (__put_user(d_off, &lastdirent->d_off))
 303                         error = -EFAULT;
 304                 else
 305                         error = count - buf.count;
 306         }
 307         fdput(f);
 308         return error;
 309 }