net/core/iovec.c

   1 /*
   2  *      iovec manipulation routines.
   3  *
   4  *
   5  *              This program is free software; you can redistribute it and/or
   6  *              modify it under the terms of the GNU General Public License
   7  *              as published by the Free Software Foundation; either version
   8  *              2 of the License, or (at your option) any later version.
   9  *
  10  *      Fixes:
  11  *              Andrew Lunn     :       Errors in iovec copying.
  12  *              Pedro Roque     :       Added memcpy_fromiovecend and
  13  *                                      csum_..._fromiovecend.
  14  *              Andi Kleen      :       fixed error handling for 2.1
  15  *              Alexey Kuznetsov:       2.1 optimisations
  16  *              Andi Kleen      :       Fix csum*fromiovecend for IPv6.
  17  */
  18
  19 #include <linux/errno.h>
  20 #include <linux/module.h>
  21 #include <linux/kernel.h>
  22 #include <linux/mm.h>
  23 #include <linux/net.h>
  24 #include <linux/in6.h>
  25 #include <asm/uaccess.h>
  26 #include <asm/byteorder.h>
  27 #include <net/checksum.h>
  28 #include <net/sock.h>
  29
  30 /*
  31  *      Verify iovec. The caller must ensure that the iovec is big enough
  32  *      to hold the message iovec.
  33  *
  34  *      Save time not doing access_ok. copy_*_user will make this work
  35  *      in any case.
  36  */
  37
  38 int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode)
  39 {
  40         int size, err, ct;
  41
  42         if (m->msg_namelen) {
  43                 if (mode == VERIFY_READ) {
  44                         err = move_addr_to_kernel(m->msg_name, m->msg_namelen,
  45                                                   address);
  46                         if (err < 0)
  47                                 return err;
  48                 }
  49                 m->msg_name = address;
  50         } else {
  51                 m->msg_name = NULL;
  52         }
  53
  54         size = m->msg_iovlen * sizeof(struct iovec);
  55         if (copy_from_user(iov, m->msg_iov, size))
  56                 return -EFAULT;
  57
  58         m->msg_iov = iov;
  59         err = 0;
  60
  61         for (ct = 0; ct < m->msg_iovlen; ct++) {
  62                 err += iov[ct].iov_len;
  63                 /*
  64                  * Goal is not to verify user data, but to prevent returning
  65                  * negative value, which is interpreted as errno.
  66                  * Overflow is still possible, but it is harmless.
  67                  */
  68                 if (err < 0)
  69                         return -EMSGSIZE;
  70         }
  71
  72         return err;
  73 }
  74
  75 /*
  76  *      Copy kernel to iovec. Returns -EFAULT on error.
  77  *
  78  *      Note: this modifies the original iovec.
  79  */
  80
  81 int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len)
  82 {
  83         while (len > 0) {
  84                 if (iov->iov_len) {
  85                         int copy = min_t(unsigned int, iov->iov_len, len);
  86                         if (copy_to_user(iov->iov_base, kdata, copy))
  87                                 return -EFAULT;
  88                         kdata += copy;
  89                         len -= copy;
  90                         iov->iov_len -= copy;
  91                         iov->iov_base += copy;
  92                 }
  93                 iov++;
  94         }
  95
  96         return 0;
  97 }
  98 EXPORT_SYMBOL(memcpy_toiovec);
  99
 100 /*
 101  *      Copy kernel to iovec. Returns -EFAULT on error.
 102  */
 103
 104 int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,
 105                       int offset, int len)
 106 {
 107         int copy;
 108         for (; len > 0; ++iov) {
 109                 /* Skip over the finished iovecs */
 110                 if (unlikely(offset >= iov->iov_len)) {
 111                         offset -= iov->iov_len;
 112                         continue;
 113                 }
 114                 copy = min_t(unsigned int, iov->iov_len - offset, len);
 115                 if (copy_to_user(iov->iov_base + offset, kdata, copy))
 116                         return -EFAULT;
 117                 offset = 0;
 118                 kdata += copy;
 119                 len -= copy;
 120         }
 121
 122         return 0;
 123 }
 124 EXPORT_SYMBOL(memcpy_toiovecend);
 125
 126 /*
 127  *      Copy iovec to kernel. Returns -EFAULT on error.
 128  *
 129  *      Note: this modifies the original iovec.
 130  */
 131
 132 int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len)
 133 {
 134         while (len > 0) {
 135                 if (iov->iov_len) {
 136                         int copy = min_t(unsigned int, len, iov->iov_len);
 137                         if (copy_from_user(kdata, iov->iov_base, copy))
 138                                 return -EFAULT;
 139                         len -= copy;
 140                         kdata += copy;
 141                         iov->iov_base += copy;
 142                         iov->iov_len -= copy;
 143                 }
 144                 iov++;
 145         }
 146
 147         return 0;
 148 }
 149 EXPORT_SYMBOL(memcpy_fromiovec);
 150
 151 /*
 152  *      Copy iovec from kernel. Returns -EFAULT on error.
 153  */
 154
 155 int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
 156                         int offset, int len)
 157 {
 158         /* Skip over the finished iovecs */
 159         while (offset >= iov->iov_len) {
 160                 offset -= iov->iov_len;
 161                 iov++;
 162         }
 163
 164         while (len > 0) {
 165                 u8 __user *base = iov->iov_base + offset;
 166                 int copy = min_t(unsigned int, len, iov->iov_len - offset);
 167
 168                 offset = 0;
 169                 if (copy_from_user(kdata, base, copy))
 170                         return -EFAULT;
 171                 len -= copy;
 172                 kdata += copy;
 173                 iov++;
 174         }
 175
 176         return 0;
 177 }
 178 EXPORT_SYMBOL(memcpy_fromiovecend);
 179
 180 /*
 181  *      And now for the all-in-one: copy and checksum from a user iovec
 182  *      directly to a datagram
 183  *      Calls to csum_partial but the last must be in 32 bit chunks
 184  *
 185  *      ip_build_xmit must ensure that when fragmenting only the last
 186  *      call to this function will be unaligned also.
 187  */
 188 int csum_partial_copy_fromiovecend(unsigned char *kdata, struct iovec *iov,
 189                                  int offset, unsigned int len, __wsum *csump)
 190 {
 191         __wsum csum = *csump;
 192         int partial_cnt = 0, err = 0;
 193
 194         /* Skip over the finished iovecs */
 195         while (offset >= iov->iov_len) {
 196                 offset -= iov->iov_len;
 197                 iov++;
 198         }
 199
 200         while (len > 0) {
 201                 u8 __user *base = iov->iov_base + offset;
 202                 int copy = min_t(unsigned int, len, iov->iov_len - offset);
 203
 204                 offset = 0;
 205
 206                 /* There is a remnant from previous iov. */
 207                 if (partial_cnt) {
 208                         int par_len = 4 - partial_cnt;
 209
 210                         /* iov component is too short ... */
 211                         if (par_len > copy) {
 212                                 if (copy_from_user(kdata, base, copy))
 213                                         goto out_fault;
 214                                 kdata += copy;
 215                                 base += copy;
 216                                 partial_cnt += copy;
 217                                 len -= copy;
 218                                 iov++;
 219                                 if (len)
 220                                         continue;
 221                                 *csump = csum_partial(kdata - partial_cnt,
 222                                                          partial_cnt, csum);
 223                                 goto out;
 224                         }
 225                         if (copy_from_user(kdata, base, par_len))
 226                                 goto out_fault;
 227                         csum = csum_partial(kdata - partial_cnt, 4, csum);
 228                         kdata += par_len;
 229                         base  += par_len;
 230                         copy  -= par_len;
 231                         len   -= par_len;
 232                         partial_cnt = 0;
 233                 }
 234
 235                 if (len > copy) {
 236                         partial_cnt = copy % 4;
 237                         if (partial_cnt) {
 238                                 copy -= partial_cnt;
 239                                 if (copy_from_user(kdata + copy, base + copy,
 240                                                 partial_cnt))
 241                                         goto out_fault;
 242                         }
 243                 }
 244
 245                 if (copy) {
 246                         csum = csum_and_copy_from_user(base, kdata, copy,
 247                                                         csum, &err);
 248                         if (err)
 249                                 goto out;
 250                 }
 251                 len   -= copy + partial_cnt;
 252                 kdata += copy + partial_cnt;
 253                 iov++;
 254         }
 255         *csump = csum;
 256 out:
 257         return err;
 258
 259 out_fault:
 260         err = -EFAULT;
 261         goto out;
 262 }
 263 EXPORT_SYMBOL(csum_partial_copy_fromiovecend);