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                 ctx->romnt = (inode->i_sb->s_flags & MS_RDONLY);
  41                 if (file->f_op->iterate) {
  42                         ctx->pos = file->f_pos;
  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                 .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(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(void * __buf, const char * name, int namlen, loff_t offset,
 166                    u64 ino, unsigned int d_type)
 167 {
 168         struct linux_dirent __user * dirent;
 169         struct getdents_callback * buf = (struct getdents_callback *) __buf;
 170         unsigned long d_ino;
 171         int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
 172                 sizeof(long));
 173
 174         buf->error = -EINVAL;   /* only used if we fail.. */
 175         if (reclen > buf->count)
 176                 return -EINVAL;
 177         d_ino = ino;
 178         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 179                 buf->error = -EOVERFLOW;
 180                 return -EOVERFLOW;
 181         }
 182         if (hide_name(name, namlen) && buf->ctx.romnt)
 183                 return 0;
 184         dirent = buf->previous;
 185         if (dirent) {
 186                 if (__put_user(offset, &dirent->d_off))
 187                         goto efault;
 188         }
 189         dirent = buf->current_dir;
 190         if (__put_user(d_ino, &dirent->d_ino))
 191                 goto efault;
 192         if (__put_user(reclen, &dirent->d_reclen))
 193                 goto efault;
 194         if (copy_to_user(dirent->d_name, name, namlen))
 195                 goto efault;
 196         if (__put_user(0, dirent->d_name + namlen))
 197                 goto efault;
 198         if (__put_user(d_type, (char __user *) dirent + reclen - 1))
 199                 goto efault;
 200         buf->previous = dirent;
 201         dirent = (void __user *)dirent + reclen;
 202         buf->current_dir = dirent;
 203         buf->count -= reclen;
 204         return 0;
 205 efault:
 206         buf->error = -EFAULT;
 207         return -EFAULT;
 208 }
 209
 210 SYSCALL_DEFINE3(getdents, unsigned int, fd,
 211                 struct linux_dirent __user *, dirent, unsigned int, count)
 212 {
 213         struct fd f;
 214         struct linux_dirent __user * lastdirent;
 215         struct getdents_callback buf = {
 216                 .ctx.actor = filldir,
 217                 .count = count,
 218                 .current_dir = dirent
 219         };
 220         int error;
 221
 222         if (!access_ok(VERIFY_WRITE, dirent, count))
 223                 return -EFAULT;
 224
 225         f = fdget(fd);
 226         if (!f.file)
 227                 return -EBADF;
 228
 229         error = iterate_dir(f.file, &buf.ctx);
 230         if (error >= 0)
 231                 error = buf.error;
 232         lastdirent = buf.previous;
 233         if (lastdirent) {
 234                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 235                         error = -EFAULT;
 236                 else
 237                         error = count - buf.count;
 238         }
 239         fdput(f);
 240         return error;
 241 }
 242
 243 struct getdents_callback64 {
 244         struct dir_context ctx;
 245         struct linux_dirent64 __user * current_dir;
 246         struct linux_dirent64 __user * previous;
 247         int count;
 248         int error;
 249 };
 250
 251 static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
 252                      u64 ino, unsigned int d_type)
 253 {
 254         struct linux_dirent64 __user *dirent;
 255         struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
 256         int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 257                 sizeof(u64));
 258
 259         buf->error = -EINVAL;   /* only used if we fail.. */
 260         if (reclen > buf->count)
 261                 return -EINVAL;
 262         if (hide_name(name, namlen) && buf->ctx.romnt)
 263                 return 0;
 264         dirent = buf->previous;
 265         if (dirent) {
 266                 if (__put_user(offset, &dirent->d_off))
 267                         goto efault;
 268         }
 269         dirent = buf->current_dir;
 270         if (__put_user(ino, &dirent->d_ino))
 271                 goto efault;
 272         if (__put_user(0, &dirent->d_off))
 273                 goto efault;
 274         if (__put_user(reclen, &dirent->d_reclen))
 275                 goto efault;
 276         if (__put_user(d_type, &dirent->d_type))
 277                 goto efault;
 278         if (copy_to_user(dirent->d_name, name, namlen))
 279                 goto efault;
 280         if (__put_user(0, dirent->d_name + namlen))
 281                 goto efault;
 282         buf->previous = dirent;
 283         dirent = (void __user *)dirent + reclen;
 284         buf->current_dir = dirent;
 285         buf->count -= reclen;
 286         return 0;
 287 efault:
 288         buf->error = -EFAULT;
 289         return -EFAULT;
 290 }
 291
 292 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 293                 struct linux_dirent64 __user *, dirent, unsigned int, count)
 294 {
 295         struct fd f;
 296         struct linux_dirent64 __user * lastdirent;
 297         struct getdents_callback64 buf = {
 298                 .ctx.actor = filldir64,
 299                 .count = count,
 300                 .current_dir = dirent
 301         };
 302         int error;
 303
 304         if (!access_ok(VERIFY_WRITE, dirent, count))
 305                 return -EFAULT;
 306
 307         f = fdget(fd);
 308         if (!f.file)
 309                 return -EBADF;
 310
 311         error = iterate_dir(f.file, &buf.ctx);
 312         if (error >= 0)
 313                 error = buf.error;
 314         lastdirent = buf.previous;
 315         if (lastdirent) {
 316                 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
 317                 if (__put_user(d_off, &lastdirent->d_off))
 318                         error = -EFAULT;
 319                 else
 320                         error = count - buf.count;
 321         }
 322         fdput(f);
 323         return error;
 324 }