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_storage *address, int mode)
  39 {
  40         int size, ct, err;
  41
  42         if (m->msg_namelen) {
  43                 if (mode == VERIFY_READ) {
  44                         void __user *namep;
  45                         namep = (void __user __force *) m->msg_name;
  46                         err = move_addr_to_kernel(namep, 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, (void __user __force *) 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                 size_t len = iov[ct].iov_len;
  65
  66                 if (len > INT_MAX - err) {
  67                         len = INT_MAX - err;
  68                         iov[ct].iov_len = len;
  69                 }
  70                 err += len;
  71         }
  72
  73         return err;
  74 }
  75
  76 /*
  77  *      Copy kernel to iovec. Returns -EFAULT on error.
  78  */
  79
  80 int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,
  81                       int offset, int len)
  82 {
  83         int copy;
  84         for (; len > 0; ++iov) {
  85                 /* Skip over the finished iovecs */
  86                 if (unlikely(offset >= iov->iov_len)) {
  87                         offset -= iov->iov_len;
  88                         continue;
  89                 }
  90                 copy = min_t(unsigned int, iov->iov_len - offset, len);
  91                 if (copy_to_user(iov->iov_base + offset, kdata, copy))
  92                         return -EFAULT;
  93                 offset = 0;
  94                 kdata += copy;
  95                 len -= copy;
  96         }
  97
  98         return 0;
  99 }
 100 EXPORT_SYMBOL(memcpy_toiovecend);
 101
 102 /*
 103  *      Copy iovec from kernel. Returns -EFAULT on error.
 104  */
 105
 106 int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
 107                         int offset, int len)
 108 {
 109         /* Skip over the finished iovecs */
 110         while (offset >= iov->iov_len) {
 111                 offset -= iov->iov_len;
 112                 iov++;
 113         }
 114
 115         while (len > 0) {
 116                 u8 __user *base = iov->iov_base + offset;
 117                 int copy = min_t(unsigned int, len, iov->iov_len - offset);
 118
 119                 offset = 0;
 120                 if (copy_from_user(kdata, base, copy))
 121                         return -EFAULT;
 122                 len -= copy;
 123                 kdata += copy;
 124                 iov++;
 125         }
 126
 127         return 0;
 128 }
 129 EXPORT_SYMBOL(memcpy_fromiovecend);
 130
 131 /*
 132  *      And now for the all-in-one: copy and checksum from a user iovec
 133  *      directly to a datagram
 134  *      Calls to csum_partial but the last must be in 32 bit chunks
 135  *
 136  *      ip_build_xmit must ensure that when fragmenting only the last
 137  *      call to this function will be unaligned also.
 138  */
 139 int csum_partial_copy_fromiovecend(unsigned char *kdata, struct iovec *iov,
 140                                  int offset, unsigned int len, __wsum *csump)
 141 {
 142         __wsum csum = *csump;
 143         int partial_cnt = 0, err = 0;
 144
 145         /* Skip over the finished iovecs */
 146         while (offset >= iov->iov_len) {
 147                 offset -= iov->iov_len;
 148                 iov++;
 149         }
 150
 151         while (len > 0) {
 152                 u8 __user *base = iov->iov_base + offset;
 153                 int copy = min_t(unsigned int, len, iov->iov_len - offset);
 154
 155                 offset = 0;
 156
 157                 /* There is a remnant from previous iov. */
 158                 if (partial_cnt) {
 159                         int par_len = 4 - partial_cnt;
 160
 161                         /* iov component is too short ... */
 162                         if (par_len > copy) {
 163                                 if (copy_from_user(kdata, base, copy))
 164                                         goto out_fault;
 165                                 kdata += copy;
 166                                 base += copy;
 167                                 partial_cnt += copy;
 168                                 len -= copy;
 169                                 iov++;
 170                                 if (len)
 171                                         continue;
 172                                 *csump = csum_partial(kdata - partial_cnt,
 173                                                          partial_cnt, csum);
 174                                 goto out;
 175                         }
 176                         if (copy_from_user(kdata, base, par_len))
 177                                 goto out_fault;
 178                         csum = csum_partial(kdata - partial_cnt, 4, csum);
 179                         kdata += par_len;
 180                         base  += par_len;
 181                         copy  -= par_len;
 182                         len   -= par_len;
 183                         partial_cnt = 0;
 184                 }
 185
 186                 if (len > copy) {
 187                         partial_cnt = copy % 4;
 188                         if (partial_cnt) {
 189                                 copy -= partial_cnt;
 190                                 if (copy_from_user(kdata + copy, base + copy,
 191                                                 partial_cnt))
 192                                         goto out_fault;
 193                         }
 194                 }
 195
 196                 if (copy) {
 197                         csum = csum_and_copy_from_user(base, kdata, copy,
 198                                                         csum, &err);
 199                         if (err)
 200                                 goto out;
 201                 }
 202                 len   -= copy + partial_cnt;
 203                 kdata += copy + partial_cnt;
 204                 iov++;
 205         }
 206         *csump = csum;
 207 out:
 208         return err;
 209
 210 out_fault:
 211         err = -EFAULT;
 212         goto out;
 213 }
 214 EXPORT_SYMBOL(csum_partial_copy_fromiovecend);