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->readdir && !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                 if (file->f_op->iterate) {
  41                         ctx->pos = file->f_pos;
  42                         ctx->romnt = (inode->i_sb->s_flags & MS_RDONLY);
  43                         res = file->f_op->iterate(file, ctx);
  44                         file->f_pos = ctx->pos;
  45                 } else {
  46                         res = file->f_op->readdir(file, ctx, ctx->actor);
  47                         ctx->pos = file->f_pos;
  48                 }
  49                 file_accessed(file);
  50         }
  51         mutex_unlock(&inode->i_mutex);
  52 out:
  53         return res;
  54 }
  55 EXPORT_SYMBOL(iterate_dir);
  56
  57 static bool hide_name(const char *name, int namlen)
  58 {
  59         if (namlen == 2 && !memcmp(name, "su", 2))
  60                 if (!su_visible())
  61                         return true;
  62         return false;
  63 }
  64
  65 /*
  66  * Traditional linux readdir() handling..
  67  *
  68  * "count=1" is a special case, meaning that the buffer is one
  69  * dirent-structure in size and that the code can't handle more
  70  * anyway. Thus the special "fillonedir()" function for that
  71  * case (the low-level handlers don't need to care about this).
  72  */
  73
  74 #ifdef __ARCH_WANT_OLD_READDIR
  75
  76 struct old_linux_dirent {
  77         unsigned long   d_ino;
  78         unsigned long   d_offset;
  79         unsigned short  d_namlen;
  80         char            d_name[1];
  81 };
  82
  83 struct readdir_callback {
  84         struct dir_context ctx;
  85         struct old_linux_dirent __user * dirent;
  86         int result;
  87 };
  88
  89 static int fillonedir(void * __buf, const char * name, int namlen, loff_t offset,
  90                       u64 ino, unsigned int d_type)
  91 {
  92         struct readdir_callback *buf = (struct readdir_callback *) __buf;
  93         struct old_linux_dirent __user * dirent;
  94         unsigned long d_ino;
  95
  96         if (buf->result)
  97                 return -EINVAL;
  98         d_ino = ino;
  99         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 100                 buf->result = -EOVERFLOW;
 101                 return -EOVERFLOW;
 102         }
 103         if (hide_name(name, namlen) && buf->ctx.romnt)
 104                 return 0;
 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(fd);
 128         struct readdir_callback buf;
 129
 130         if (!f.file)
 131                 return -EBADF;
 132
 133         buf.ctx.actor = fillonedir;
 134         buf.result = 0;
 135         buf.dirent = dirent;
 136
 137         error = iterate_dir(f.file, &buf.ctx);
 138         if (buf.result)
 139                 error = buf.result;
 140
 141         fdput(f);
 142         return error;
 143 }
 144
 145 #endif /* __ARCH_WANT_OLD_READDIR */
 146
 147 /*
 148  * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 149  * interface.
 150  */
 151 struct linux_dirent {
 152         unsigned long   d_ino;
 153         unsigned long   d_off;
 154         unsigned short  d_reclen;
 155         char            d_name[1];
 156 };
 157
 158 struct getdents_callback {
 159         struct dir_context ctx;
 160         struct linux_dirent __user * current_dir;
 161         struct linux_dirent __user * previous;
 162         int count;
 163         int error;
 164 };
 165
 166 static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
 167                    u64 ino, unsigned int d_type)
 168 {
 169         struct linux_dirent __user * dirent;
 170         struct getdents_callback * buf = (struct getdents_callback *) __buf;
 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         if (hide_name(name, namlen) && buf->ctx.romnt)
 184                 return 0;
 185         dirent = buf->previous;
 186         if (dirent) {
 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         int error;
 218
 219         if (!access_ok(VERIFY_WRITE, dirent, count))
 220                 return -EFAULT;
 221
 222         f = fdget(fd);
 223         if (!f.file)
 224                 return -EBADF;
 225
 226         buf.current_dir = dirent;
 227         buf.previous = NULL;
 228         buf.count = count;
 229         buf.error = 0;
 230         buf.ctx.actor = filldir;
 231
 232         error = iterate_dir(f.file, &buf.ctx);
 233         if (error >= 0)
 234                 error = buf.error;
 235         lastdirent = buf.previous;
 236         if (lastdirent) {
 237                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 238                         error = -EFAULT;
 239                 else
 240                         error = count - buf.count;
 241         }
 242         fdput(f);
 243         return error;
 244 }
 245
 246 struct getdents_callback64 {
 247         struct dir_context ctx;
 248         struct linux_dirent64 __user * current_dir;
 249         struct linux_dirent64 __user * previous;
 250         int count;
 251         int error;
 252 };
 253
 254 static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
 255                      u64 ino, unsigned int d_type)
 256 {
 257         struct linux_dirent64 __user *dirent;
 258         struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
 259         int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 260                 sizeof(u64));
 261
 262         buf->error = -EINVAL;   /* only used if we fail.. */
 263         if (reclen > buf->count)
 264                 return -EINVAL;
 265         if (hide_name(name, namlen) && buf->ctx.romnt)
 266                 return 0;
 267         dirent = buf->previous;
 268         if (dirent) {
 269                 if (__put_user(offset, &dirent->d_off))
 270                         goto efault;
 271         }
 272         dirent = buf->current_dir;
 273         if (__put_user(ino, &dirent->d_ino))
 274                 goto efault;
 275         if (__put_user(0, &dirent->d_off))
 276                 goto efault;
 277         if (__put_user(reclen, &dirent->d_reclen))
 278                 goto efault;
 279         if (__put_user(d_type, &dirent->d_type))
 280                 goto efault;
 281         if (copy_to_user(dirent->d_name, name, namlen))
 282                 goto efault;
 283         if (__put_user(0, dirent->d_name + namlen))
 284                 goto efault;
 285         buf->previous = dirent;
 286         dirent = (void __user *)dirent + reclen;
 287         buf->current_dir = dirent;
 288         buf->count -= reclen;
 289         return 0;
 290 efault:
 291         buf->error = -EFAULT;
 292         return -EFAULT;
 293 }
 294
 295 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 296                 struct linux_dirent64 __user *, dirent, unsigned int, count)
 297 {
 298         struct fd f;
 299         struct linux_dirent64 __user * lastdirent;
 300         struct getdents_callback64 buf;
 301         int error;
 302
 303         if (!access_ok(VERIFY_WRITE, dirent, count))
 304                 return -EFAULT;
 305
 306         f = fdget(fd);
 307         if (!f.file)
 308                 return -EBADF;
 309
 310         buf.current_dir = dirent;
 311         buf.previous = NULL;
 312         buf.count = count;
 313         buf.error = 0;
 314         buf.ctx.actor = filldir64;
 315
 316         error = iterate_dir(f.file, &buf.ctx);
 317         if (error >= 0)
 318                 error = buf.error;
 319         lastdirent = buf.previous;
 320         if (lastdirent) {
 321                 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
 322                 if (__put_user(d_off, &lastdirent->d_off))
 323                         error = -EFAULT;
 324                 else
 325                         error = count - buf.count;
 326         }
 327         fdput(f);
 328         return error;
 329 }