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/sched.h>
  22 #include <linux/kernel.h>
  23 #include <linux/mm.h>
  24 #include <linux/slab.h>
  25 #include <linux/net.h>
  26 #include <linux/in6.h>
  27 #include <asm/uaccess.h>
  28 #include <asm/byteorder.h>
  29 #include <net/checksum.h>
  30 #include <net/sock.h>
  31
  32 /*
  33  *      Verify iovec. The caller must ensure that the iovec is big enough
  34  *      to hold the message iovec.
  35  *
  36  *      Save time not doing access_ok. copy_*_user will make this work
  37  *      in any case.
  38  */
  39
  40 int verify_iovec(struct msghdr *m, struct iovec *iov, char *address, int mode)
  41 {
  42         int size, err, ct;
  43
  44         if (m->msg_namelen) {
  45                 if (mode == VERIFY_READ) {
  46                         err = move_addr_to_kernel(m->msg_name, m->msg_namelen,
  47                                                   address);
  48                         if (err < 0)
  49                                 return err;
  50                 }
  51                 m->msg_name = address;
  52         } else {
  53                 m->msg_name = NULL;
  54         }
  55
  56         size = m->msg_iovlen * sizeof(struct iovec);
  57         if (copy_from_user(iov, m->msg_iov, size))
  58                 return -EFAULT;
  59
  60         m->msg_iov = iov;
  61         err = 0;
  62
  63         for (ct = 0; ct < m->msg_iovlen; ct++) {
  64                 err += iov[ct].iov_len;
  65                 /*
  66                  * Goal is not to verify user data, but to prevent returning
  67                  * negative value, which is interpreted as errno.
  68                  * Overflow is still possible, but it is harmless.
  69                  */
  70                 if (err < 0)
  71                         return -EMSGSIZE;
  72         }
  73
  74         return err;
  75 }
  76
  77 /*
  78  *      Copy kernel to iovec. Returns -EFAULT on error.
  79  *
  80  *      Note: this modifies the original iovec.
  81  */
  82
  83 int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len)
  84 {
  85         while (len > 0) {
  86                 if (iov->iov_len) {
  87                         int copy = min_t(unsigned int, iov->iov_len, len);
  88                         if (copy_to_user(iov->iov_base, kdata, copy))
  89                                 return -EFAULT;
  90                         kdata += copy;
  91                         len -= copy;
  92                         iov->iov_len -= copy;
  93                         iov->iov_base += copy;
  94                 }
  95                 iov++;
  96         }
  97
  98         return 0;
  99 }
 100
 101 /*
 102  *      Copy iovec to kernel. Returns -EFAULT on error.
 103  *
 104  *      Note: this modifies the original iovec.
 105  */
 106
 107 int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len)
 108 {
 109         while (len > 0) {
 110                 if (iov->iov_len) {
 111                         int copy = min_t(unsigned int, len, iov->iov_len);
 112                         if (copy_from_user(kdata, iov->iov_base, copy))
 113                                 return -EFAULT;
 114                         len -= copy;
 115                         kdata += copy;
 116                         iov->iov_base += copy;
 117                         iov->iov_len -= copy;
 118                 }
 119                 iov++;
 120         }
 121
 122         return 0;
 123 }
 124
 125 /*
 126  *      For use with ip_build_xmit
 127  */
 128 int memcpy_fromiovecend(unsigned char *kdata, struct iovec *iov, int offset,
 129                         int len)
 130 {
 131         /* Skip over the finished iovecs */
 132         while (offset >= iov->iov_len) {
 133                 offset -= iov->iov_len;
 134                 iov++;
 135         }
 136
 137         while (len > 0) {
 138                 u8 __user *base = iov->iov_base + offset;
 139                 int copy = min_t(unsigned int, len, iov->iov_len - offset);
 140
 141                 offset = 0;
 142                 if (copy_from_user(kdata, base, copy))
 143                         return -EFAULT;
 144                 len -= copy;
 145                 kdata += copy;
 146                 iov++;
 147         }
 148
 149         return 0;
 150 }
 151
 152 /*
 153  *      And now for the all-in-one: copy and checksum from a user iovec
 154  *      directly to a datagram
 155  *      Calls to csum_partial but the last must be in 32 bit chunks
 156  *
 157  *      ip_build_xmit must ensure that when fragmenting only the last
 158  *      call to this function will be unaligned also.
 159  */
 160 int csum_partial_copy_fromiovecend(unsigned char *kdata, struct iovec *iov,
 161                                  int offset, unsigned int len, int *csump)
 162 {
 163         int csum = *csump;
 164         int partial_cnt = 0, err = 0;
 165
 166         /* Skip over the finished iovecs */
 167         while (offset >= iov->iov_len) {
 168                 offset -= iov->iov_len;
 169                 iov++;
 170         }
 171
 172         while (len > 0) {
 173                 u8 __user *base = iov->iov_base + offset;
 174                 int copy = min_t(unsigned int, len, iov->iov_len - offset);
 175
 176                 offset = 0;
 177
 178                 /* There is a remnant from previous iov. */
 179                 if (partial_cnt) {
 180                         int par_len = 4 - partial_cnt;
 181
 182                         /* iov component is too short ... */
 183                         if (par_len > copy) {
 184                                 if (copy_from_user(kdata, base, copy))
 185                                         goto out_fault;
 186                                 kdata += copy;
 187                                 base += copy;
 188                                 partial_cnt += copy;
 189                                 len -= copy;
 190                                 iov++;
 191                                 if (len)
 192                                         continue;
 193                                 *csump = csum_partial(kdata - partial_cnt,
 194                                                          partial_cnt, csum);
 195                                 goto out;
 196                         }
 197                         if (copy_from_user(kdata, base, par_len))
 198                                 goto out_fault;
 199                         csum = csum_partial(kdata - partial_cnt, 4, csum);
 200                         kdata += par_len;
 201                         base  += par_len;
 202                         copy  -= par_len;
 203                         len   -= par_len;
 204                         partial_cnt = 0;
 205                 }
 206
 207                 if (len > copy) {
 208                         partial_cnt = copy % 4;
 209                         if (partial_cnt) {
 210                                 copy -= partial_cnt;
 211                                 if (copy_from_user(kdata + copy, base + copy,
 212                                                 partial_cnt))
 213                                         goto out_fault;
 214                         }
 215                 }
 216
 217                 if (copy) {
 218                         csum = csum_and_copy_from_user(base, kdata, copy,
 219                                                         csum, &err);
 220                         if (err)
 221                                 goto out;
 222                 }
 223                 len   -= copy + partial_cnt;
 224                 kdata += copy + partial_cnt;
 225                 iov++;
 226         }
 227         *csump = csum;
 228 out:
 229         return err;
 230
 231 out_fault:
 232         err = -EFAULT;
 233         goto out;
 234 }
 235
 236 EXPORT_SYMBOL(csum_partial_copy_fromiovecend);
 237 EXPORT_SYMBOL(memcpy_fromiovec);
 238 EXPORT_SYMBOL(memcpy_fromiovecend);
 239 EXPORT_SYMBOL(memcpy_toiovec);