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>

1 files changed, 49 insertions, 0 deletions

diff --git a/net/socket.c b/net/socket.c
index 63b53af7379b..fbf80f9fb057 100644
--- 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: