socket: fix struct ifreq size in compat ioctl

As reported by Reobert O'Callahan, since Viro's commit to kill
dev_ifsioc() we attempt to copy too much data in compat mode,
which may lead to EFAULT when the 32-bit version of struct ifreq
sits at/near the end of a page boundary, and the next page isn't
mapped.

Fix this by passing the approprate compat/non-compat size to copy
and using that, as before the dev_ifsioc() removal. This works
because only the embedded "struct ifmap" has different size, and
this is only used in SIOCGIFMAP/SIOCSIFMAP which has a different
handler. All other parts of the union are naturally compatible.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=199469.

Fixes: bf4405737f9f ("kill dev_ifsioc()")
Reported-by: Robert O'Callahan <robert@ocallahan.org>
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 e6945e318f0285441c0095903e099cb272fa78ec..01f3f8f32d6f927fd77bac5920ab5d8339c2f6af 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -941,7 +941,8 @@ void dlci_ioctl_set(int (*hook) (unsigned int, void __user *))
 EXPORT_SYMBOL(dlci_ioctl_set);
 
 static long sock_do_ioctl(struct net *net, struct socket *sock,
-                                unsigned int cmd, unsigned long arg)
+                         unsigned int cmd, unsigned long arg,
+                         unsigned int ifreq_size)
 {
        int err;
        void __user *argp = (void __user *)arg;
@@ -967,11 +968,11 @@ static long sock_do_ioctl(struct net *net, struct socket *sock,
        } else {
                struct ifreq ifr;
                bool need_copyout;
-               if (copy_from_user(&ifr, argp, sizeof(struct ifreq)))
+               if (copy_from_user(&ifr, argp, ifreq_size))
                        return -EFAULT;
                err = dev_ioctl(net, cmd, &ifr, &need_copyout);
                if (!err && need_copyout)
-                       if (copy_to_user(argp, &ifr, sizeof(struct ifreq)))
+                       if (copy_to_user(argp, &ifr, ifreq_size))
                                return -EFAULT;
        }
        return err;
@@ -1070,7 +1071,8 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
                        err = open_related_ns(&net->ns, get_net_ns);
                        break;
                default:
-                       err = sock_do_ioctl(net, sock, cmd, arg);
+                       err = sock_do_ioctl(net, sock, cmd, arg,
+                                           sizeof(struct ifreq));
                        break;
                }
        return err;
@@ -2750,7 +2752,8 @@ static int do_siocgstamp(struct net *net, struct socket *sock,
        int err;
 
        set_fs(KERNEL_DS);
-       err = sock_do_ioctl(net, sock, cmd, (unsigned long)&ktv);
+       err = sock_do_ioctl(net, sock, cmd, (unsigned long)&ktv,
+                           sizeof(struct compat_ifreq));
        set_fs(old_fs);
        if (!err)
                err = compat_put_timeval(&ktv, up);
@@ -2766,7 +2769,8 @@ static int do_siocgstampns(struct net *net, struct socket *sock,
        int err;
 
        set_fs(KERNEL_DS);
-       err = sock_do_ioctl(net, sock, cmd, (unsigned long)&kts);
+       err = sock_do_ioctl(net, sock, cmd, (unsigned long)&kts,
+                           sizeof(struct compat_ifreq));
        set_fs(old_fs);
        if (!err)
                err = compat_put_timespec(&kts, up);
@@ -3072,7 +3076,8 @@ static int routing_ioctl(struct net *net, struct socket *sock,
        }
 
        set_fs(KERNEL_DS);
-       ret = sock_do_ioctl(net, sock, cmd, (unsigned long) r);
+       ret = sock_do_ioctl(net, sock, cmd, (unsigned long) r,
+                           sizeof(struct compat_ifreq));
        set_fs(old_fs);
 
 out:
@@ -3185,7 +3190,8 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
        case SIOCBONDSETHWADDR:
        case SIOCBONDCHANGEACTIVE:
        case SIOCGIFNAME:
-               return sock_do_ioctl(net, sock, cmd, arg);
+               return sock_do_ioctl(net, sock, cmd, arg,
+                                    sizeof(struct compat_ifreq));
        }
 
        return -ENOIOCTLCMD;