net: separate SIOCGIFCONF handling from dev_ioctl()

Only two of dev_ioctl() callers may pass SIOCGIFCONF to it.
Separating that codepath from the rest of dev_ioctl() allows both
to simplify dev_ioctl() itself (all other cases work with struct ifreq *)
*and* seriously simplify the compat side of that beast: all it takes
is passing to inet_gifconf() an extra argument - the size of individual
records (sizeof(struct ifreq) or sizeof(struct compat_ifreq)).  With
dev_ifconf() called directly from sock_do_ioctl()/compat_dev_ifconf()
that's easy to arrange.

As the result, compat side of SIOCGIFCONF doesn't need any
allocations, copy_in_user() back and forth, etc.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 42 insertions, 86 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 581495f4e487..df5565d0369c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2761,7 +2761,8 @@ static inline bool dev_validate_header(const struct net_device *dev,
         return false;
 }
 
-typedef int gifconf_func_t(struct net_device * dev, char __user * bufptr, int len);
+typedef int gifconf_func_t(struct net_device * dev, char __user * bufptr,
+                           int len, int size);
 int register_gifconf(unsigned int family, gifconf_func_t *gifconf);
 static inline int unregister_gifconf(unsigned int family)
 {
@@ -3315,6 +3316,7 @@ void netdev_rx_handler_unregister(struct net_device *dev);
 
 bool dev_valid_name(const char *name);
 int dev_ioctl(struct net *net, unsigned int cmd, void __user *);
+int dev_ifconf(struct net *net, struct ifconf *, int);
 int dev_ethtool(struct net *net, struct ifreq *);
 unsigned int dev_get_flags(const struct net_device *);
 int __dev_change_flags(struct net_device *, unsigned int flags);
diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 7e690d0ccd05..5cdec23dd28e 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -66,9 +66,8 @@ EXPORT_SYMBOL(register_gifconf);
  *      Thus we will need a 'compatibility mode'.
  */
 
-static int dev_ifconf(struct net *net, char __user *arg)
+int dev_ifconf(struct net *net, struct ifconf *ifc, int size)
 {
-        struct ifconf ifc;
         struct net_device *dev;
         char __user *pos;
         int len;
@@ -79,11 +78,8 @@ static int dev_ifconf(struct net *net, char __user *arg)
          *      Fetch the caller's info block.
          */
 
-        if (copy_from_user(&ifc, arg, sizeof(struct ifconf)))
-                return -EFAULT;
-
-        pos = ifc.ifc_buf;
-        len = ifc.ifc_len;
+        pos = ifc->ifc_buf;
+        len = ifc->ifc_len;
 
         /*
          *      Loop over the interfaces, and write an info block for each.
@@ -95,10 +91,10 @@ static int dev_ifconf(struct net *net, char __user *arg)
                         if (gifconf_list[i]) {
                                 int done;
                                 if (!pos)
-                                        done = gifconf_list[i](dev, NULL, 0);
+                                        done = gifconf_list[i](dev, NULL, 0, size);
                                 else
                                         done = gifconf_list[i](dev, pos + total,
-                                                               len - total);
+                                                               len - total, size);
                                 if (done < 0)
                                         return -EFAULT;
                                 total += done;
@@ -109,12 +105,12 @@ static int dev_ifconf(struct net *net, char __user *arg)
         /*
          *      All done.  Write the updated control block back to the caller.
          */
-        ifc.ifc_len = total;
+        ifc->ifc_len = total;
 
         /*
          *      Both BSD and Solaris return 0 here, so we do too.
          */
-        return copy_to_user(arg, &ifc, sizeof(struct ifconf)) ? -EFAULT : 0;
+        return 0;
 }
 
 /*
@@ -412,17 +408,6 @@ int dev_ioctl(struct net *net, unsigned int cmd, void __user *arg)
         int ret;
         char *colon;
 
-        /* One special case: SIOCGIFCONF takes ifconf argument
-           and requires shared lock, because it sleeps writing
-           to user space.
-         */
-
-        if (cmd == SIOCGIFCONF) {
-                rtnl_lock();
-                ret = dev_ifconf(net, (char __user *) arg);
-                rtnl_unlock();
-                return ret;
-        }
         if (cmd == SIOCGIFNAME)
                 return dev_ifname(net, (struct ifreq __user *)arg);
 
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 7a93359fbc72..1771549d2438 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1188,22 +1188,25 @@ rarok:
         goto out;
 }
 
-static int inet_gifconf(struct net_device *dev, char __user *buf, int len)
+static int inet_gifconf(struct net_device *dev, char __user *buf, int len, int size)
 {
         struct in_device *in_dev = __in_dev_get_rtnl(dev);
         struct in_ifaddr *ifa;
         struct ifreq ifr;
         int done = 0;
 
+        if (WARN_ON(size > sizeof(struct ifreq)))
+                goto out;
+
         if (!in_dev)
                 goto out;
 
         for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) {
                 if (!buf) {
-                        done += sizeof(ifr);
+                        done += size;
                         continue;
                 }
-                if (len < (int) sizeof(ifr))
+                if (len < size)
                         break;
                 memset(&ifr, 0, sizeof(struct ifreq));
                 strcpy(ifr.ifr_name, ifa->ifa_label);
@@ -1212,13 +1215,12 @@ static int inet_gifconf(struct net_device *dev, char __user *buf, int len)
                 (*(struct sockaddr_in *)&ifr.ifr_addr).sin_addr.s_addr =
                                                                 ifa->ifa_local;
 
-                if (copy_to_user(buf, &ifr, sizeof(struct ifreq))) {
+                if (copy_to_user(buf + done, &ifr, size)) {
                         done = -EFAULT;
                         break;
                 }
-                buf  += sizeof(struct ifreq);
-                len  -= sizeof(struct ifreq);
-                done += sizeof(struct ifreq);
+                len  -= size;
+                done += size;
         }
 out:
         return done;
diff --git a/net/socket.c b/net/socket.c
index 1536515b6437..96e5b23a2a2e 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -961,10 +961,22 @@ static long sock_do_ioctl(struct net *net, struct socket *sock,
          * If this ioctl is unknown try to hand it down
          * to the NIC driver.
          */
-        if (err == -ENOIOCTLCMD)
-                err = dev_ioctl(net, cmd, argp);
+        if (err != -ENOIOCTLCMD)
+                return err;
 
-        return err;
+        if (cmd == SIOCGIFCONF) {
+                struct ifconf ifc;
+                if (copy_from_user(&ifc, argp, sizeof(struct ifconf)))
+                        return -EFAULT;
+                rtnl_lock();
+                err = dev_ifconf(net, &ifc, sizeof(struct ifreq));
+                rtnl_unlock();
+                if (!err && copy_to_user(argp, &ifc, sizeof(struct ifconf)))
+                        err = -EFAULT;
+                return err;
+        }
+
+        return dev_ioctl(net, cmd, argp);
 }
 
 /*
@@ -2673,70 +2685,25 @@ static int dev_ifname32(struct net *net, struct compat_ifreq __user *uifr32)
         return 0;
 }
 
-static int dev_ifconf(struct net *net, struct compat_ifconf __user *uifc32)
+static int compat_dev_ifconf(struct net *net, struct compat_ifconf __user *uifc32)
 {
         struct compat_ifconf ifc32;
         struct ifconf ifc;
-        struct ifconf __user *uifc;
-        struct compat_ifreq __user *ifr32;
-        struct ifreq __user *ifr;
-        unsigned int i, j;
         int err;
 
         if (copy_from_user(&ifc32, uifc32, sizeof(struct compat_ifconf)))
                 return -EFAULT;
 
-        memset(&ifc, 0, sizeof(ifc));
-        if (ifc32.ifcbuf == 0) {
-                ifc32.ifc_len = 0;
-                ifc.ifc_len = 0;
-                ifc.ifc_req = NULL;
-                uifc = compat_alloc_user_space(sizeof(struct ifconf));
-        } else {
-                size_t len = ((ifc32.ifc_len / sizeof(struct compat_ifreq)) + 1) *
-                        sizeof(struct ifreq);
-                uifc = compat_alloc_user_space(sizeof(struct ifconf) + len);
-                ifc.ifc_len = len;
-                ifr = ifc.ifc_req = (void __user *)(uifc + 1);
-                ifr32 = compat_ptr(ifc32.ifcbuf);
-                for (i = 0; i < ifc32.ifc_len; i += sizeof(struct compat_ifreq)) {
-                        if (copy_in_user(ifr, ifr32, sizeof(struct compat_ifreq)))
-                                return -EFAULT;
-                        ifr++;
-                        ifr32++;
-                }
-        }
-        if (copy_to_user(uifc, &ifc, sizeof(struct ifconf)))
-                return -EFAULT;
+        ifc.ifc_len = ifc32.ifc_len;
+        ifc.ifc_req = compat_ptr(ifc32.ifcbuf);
 
-        err = dev_ioctl(net, SIOCGIFCONF, uifc);
+        rtnl_lock();
+        err = dev_ifconf(net, &ifc, sizeof(struct compat_ifreq));
+        rtnl_unlock();
         if (err)
                 return err;
 
-        if (copy_from_user(&ifc, uifc, sizeof(struct ifconf)))
-                return -EFAULT;
-
-        ifr = ifc.ifc_req;
-        ifr32 = compat_ptr(ifc32.ifcbuf);
-        for (i = 0, j = 0;
-             i + sizeof(struct compat_ifreq) <= ifc32.ifc_len && j < ifc.ifc_len;
-             i += sizeof(struct compat_ifreq), j += sizeof(struct ifreq)) {
-                if (copy_in_user(ifr32, ifr, sizeof(struct compat_ifreq)))
-                        return -EFAULT;
-                ifr32++;
-                ifr++;
-        }
-
-        if (ifc32.ifcbuf == 0) {
-                /* Translate from 64-bit structure multiple to
-                 * a 32-bit one.
-                 */
-                i = ifc.ifc_len;
-                i = ((i / sizeof(struct ifreq)) * sizeof(struct compat_ifreq));
-                ifc32.ifc_len = i;
-        } else {
-                ifc32.ifc_len = i;
-        }
+        ifc32.ifc_len = ifc.ifc_len;
         if (copy_to_user(uifc32, &ifc32, sizeof(struct compat_ifconf)))
                 return -EFAULT;
 
@@ -3133,7 +3100,7 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
         case SIOCGIFNAME:
                 return dev_ifname32(net, argp);
         case SIOCGIFCONF:
-                return dev_ifconf(net, argp);
+                return compat_dev_ifconf(net, argp);
         case SIOCETHTOOL:
                 return ethtool_ioctl(net, argp);
         case SIOCWANDEV: