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                 if (m->msg_name)
  52                         m->msg_name = address;
  53         } else {
  54                 m->msg_name = NULL;
  55         }
  56
  57         size = m->msg_iovlen * sizeof(struct iovec);
  58         if (copy_from_user(iov, (void __user __force *) m->msg_iov, size))
  59                 return -EFAULT;
  60
  61         m->msg_iov = iov;
  62         err = 0;
  63
  64         for (ct = 0; ct < m->msg_iovlen; ct++) {
  65                 size_t len = iov[ct].iov_len;
  66
  67                 if (len > INT_MAX - err) {
  68                         len = INT_MAX - err;
  69                         iov[ct].iov_len = len;
  70                 }
  71                 err += len;
  72         }
  73
  74         return err;
  75 }
  76
  77 /*
  78  *      And now for the all-in-one: copy and checksum from a user iovec
  79  *      directly to a datagram
  80  *      Calls to csum_partial but the last must be in 32 bit chunks
  81  *
  82  *      ip_build_xmit must ensure that when fragmenting only the last
  83  *      call to this function will be unaligned also.
  84  */
  85 int csum_partial_copy_fromiovecend(unsigned char *kdata, struct iovec *iov,
  86                                  int offset, unsigned int len, __wsum *csump)
  87 {
  88         __wsum csum = *csump;
  89         int partial_cnt = 0, err = 0;
  90
  91         /* Skip over the finished iovecs */
  92         while (offset >= iov->iov_len) {
  93                 offset -= iov->iov_len;
  94                 iov++;
  95         }
  96
  97         while (len > 0) {
  98                 u8 __user *base = iov->iov_base + offset;
  99                 int copy = min_t(unsigned int, len, iov->iov_len - offset);
 100
 101                 offset = 0;
 102
 103                 /* There is a remnant from previous iov. */
 104                 if (partial_cnt) {
 105                         int par_len = 4 - partial_cnt;
 106
 107                         /* iov component is too short ... */
 108                         if (par_len > copy) {
 109                                 if (copy_from_user(kdata, base, copy))
 110                                         goto out_fault;
 111                                 kdata += copy;
 112                                 base += copy;
 113                                 partial_cnt += copy;
 114                                 len -= copy;
 115                                 iov++;
 116                                 if (len)
 117                                         continue;
 118                                 *csump = csum_partial(kdata - partial_cnt,
 119                                                          partial_cnt, csum);
 120                                 goto out;
 121                         }
 122                         if (copy_from_user(kdata, base, par_len))
 123                                 goto out_fault;
 124                         csum = csum_partial(kdata - partial_cnt, 4, csum);
 125                         kdata += par_len;
 126                         base  += par_len;
 127                         copy  -= par_len;
 128                         len   -= par_len;
 129                         partial_cnt = 0;
 130                 }
 131
 132                 if (len > copy) {
 133                         partial_cnt = copy % 4;
 134                         if (partial_cnt) {
 135                                 copy -= partial_cnt;
 136                                 if (copy_from_user(kdata + copy, base + copy,
 137                                                 partial_cnt))
 138                                         goto out_fault;
 139                         }
 140                 }
 141
 142                 if (copy) {
 143                         csum = csum_and_copy_from_user(base, kdata, copy,
 144                                                         csum, &err);
 145                         if (err)
 146                                 goto out;
 147                 }
 148                 len   -= copy + partial_cnt;
 149                 kdata += copy + partial_cnt;
 150                 iov++;
 151         }
 152         *csump = csum;
 153 out:
 154         return err;
 155
 156 out_fault:
 157         err = -EFAULT;
 158         goto out;
 159 }
 160 EXPORT_SYMBOL(csum_partial_copy_fromiovecend);
 161
 162 unsigned long iov_pages(const struct iovec *iov, int offset,
 163                         unsigned long nr_segs)
 164 {
 165         unsigned long seg, base;
 166         int pages = 0, len, size;
 167
 168         while (nr_segs && (offset >= iov->iov_len)) {
 169                 offset -= iov->iov_len;
 170                 ++iov;
 171                 --nr_segs;
 172         }
 173
 174         for (seg = 0; seg < nr_segs; seg++) {
 175                 base = (unsigned long)iov[seg].iov_base + offset;
 176                 len = iov[seg].iov_len - offset;
 177                 size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
 178                 pages += size;
 179                 offset = 0;
 180         }
 181
 182         return pages;
 183 }
 184 EXPORT_SYMBOL(iov_pages);