Revert "kill dev_ifsioc()"

This reverts commit bf4405737f9f ("kill dev_ifsioc()").

This wasn't really unused as implied by the original commit,
it still handles the copy to/from user differently, and the
commit thus caused issues such as
  https://bugzilla.kernel.org/show_bug.cgi?id=199469
and
  https://bugzilla.kernel.org/show_bug.cgi?id=202273

However, deviating from a strict revert, rename dev_ifsioc()
to compat_ifreq_ioctl() to be clearer as to its purpose and
add a comment.

Cc: stable@vger.kernel.org
Fixes: bf4405737f9f ("kill dev_ifsioc()")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/socket.c b/net/socket.c
index 63b53af..fbf80f9 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -2990,6 +2990,53 @@ static int compat_ifr_data_ioctl(struct net *net, unsigned int cmd,
        return dev_ioctl(net, cmd, &ifreq, NULL);
 }
 
+static int compat_ifreq_ioctl(struct net *net, struct socket *sock,
+                             unsigned int cmd,
+                             struct compat_ifreq __user *uifr32)
+{
+       struct ifreq __user *uifr;
+       int err;
+
+       /* Handle the fact that while struct ifreq has the same *layout* on
+        * 32/64 for everything but ifreq::ifru_ifmap and ifreq::ifru_data,
+        * which are handled elsewhere, it still has different *size* due to
+        * ifreq::ifru_ifmap (which is 16 bytes on 32 bit, 24 bytes on 64-bit,
+        * resulting in struct ifreq being 32 and 40 bytes respectively).
+        * As a result, if the struct happens to be at the end of a page and
+        * the next page isn't readable/writable, we get a fault. To prevent
+        * that, copy back and forth to the full size.
+        */
+
+       uifr = compat_alloc_user_space(sizeof(*uifr));
+       if (copy_in_user(uifr, uifr32, sizeof(*uifr32)))
+               return -EFAULT;
+
+       err = sock_do_ioctl(net, sock, cmd, (unsigned long)uifr);
+
+       if (!err) {
+               switch (cmd) {
+               case SIOCGIFFLAGS:
+               case SIOCGIFMETRIC:
+               case SIOCGIFMTU:
+               case SIOCGIFMEM:
+               case SIOCGIFHWADDR:
+               case SIOCGIFINDEX:
+               case SIOCGIFADDR:
+               case SIOCGIFBRDADDR:
+               case SIOCGIFDSTADDR:
+               case SIOCGIFNETMASK:
+               case SIOCGIFPFLAGS:
+               case SIOCGIFTXQLEN:
+               case SIOCGMIIPHY:
+               case SIOCGMIIREG:
+                       if (copy_in_user(uifr32, uifr, sizeof(*uifr32)))
+                               err = -EFAULT;
+                       break;
+               }
+       }
+       return err;
+}
+
 static int compat_sioc_ifmap(struct net *net, unsigned int cmd,
                        struct compat_ifreq __user *uifr32)
 {
@@ -3209,6 +3256,8 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
        case SIOCGMIIPHY:
        case SIOCGMIIREG:
        case SIOCSMIIREG:
+               return compat_ifreq_ioctl(net, sock, cmd, argp);
+
        case SIOCSARP:
        case SIOCGARP:
        case SIOCDARP: