netdevice: Fix promiscuity and allmulti overflow

Max of promiscuity and allmulti plus positive @inc can cause overflow.
Fox example: when allmulti=0xFFFFFFFF, any caller give dev_set_allmulti() a
positive @inc will cause allmulti be off.
This is not what we want, though it's rare case.
The fix is that only negative @inc will cause allmulti or promiscuity be off
and when any caller makes the counters touch the roof, we return error.

Change of v2:
Change void function dev_set_promiscuity/allmulti to return int.
So callers can get the overflow error.
Caller's fix will be done later.

Change of v3:
1. Since we return error to caller, we don't need to print KERN_ERROR,
KERN_WARNING is enough.
2. In dev_set_promiscuity(), if __dev_set_promiscuity() failed, we
return at once.

Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 45 insertions, 10 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 0e45742e7158..a495f712d38c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2771,16 +2771,29 @@ int netdev_set_master(struct net_device *slave, struct net_device *master)
         return 0;
 }
 
-static void __dev_set_promiscuity(struct net_device *dev, int inc)
+static int __dev_set_promiscuity(struct net_device *dev, int inc)
 {
         unsigned short old_flags = dev->flags;
 
         ASSERT_RTNL();
 
-        if ((dev->promiscuity += inc) == 0)
-                dev->flags &= ~IFF_PROMISC;
-        else
-                dev->flags |= IFF_PROMISC;
+        dev->flags |= IFF_PROMISC;
+        dev->promiscuity += inc;
+        if (dev->promiscuity == 0) {
+                /*
+                 * Avoid overflow.
+                 * If inc causes overflow, untouch promisc and return error.
+                 */
+                if (inc < 0)
+                        dev->flags &= ~IFF_PROMISC;
+                else {
+                        dev->promiscuity -= inc;
+                        printk(KERN_WARNING "%s: promiscuity touches roof, "
+                                "set promiscuity failed, promiscuity feature "
+                                "of device might be broken.\n", dev->name);
+                        return -EOVERFLOW;
+                }
+        }
         if (dev->flags != old_flags) {
                 printk(KERN_INFO "device %s %s promiscuous mode\n",
                        dev->name, (dev->flags & IFF_PROMISC) ? "entered" :
@@ -2798,6 +2811,7 @@ static void __dev_set_promiscuity(struct net_device *dev, int inc)
                 if (dev->change_rx_flags)
                         dev->change_rx_flags(dev, IFF_PROMISC);
         }
+        return 0;
 }
 
 /**
@@ -2809,14 +2823,19 @@ static void __dev_set_promiscuity(struct net_device *dev, int inc)
  *      remains above zero the interface remains promiscuous. Once it hits zero
  *      the device reverts back to normal filtering operation. A negative inc
  *      value is used to drop promiscuity on the device.
+ *      Return 0 if successful or a negative errno code on error.
  */
-void dev_set_promiscuity(struct net_device *dev, int inc)
+int dev_set_promiscuity(struct net_device *dev, int inc)
 {
         unsigned short old_flags = dev->flags;
+        int err;
 
-        __dev_set_promiscuity(dev, inc);
+        err = __dev_set_promiscuity(dev, inc);
+        if (!err)
+                return err;
         if (dev->flags != old_flags)
                 dev_set_rx_mode(dev);
+        return err;
 }
 
 /**
@@ -2829,22 +2848,38 @@ void dev_set_promiscuity(struct net_device *dev, int inc)
  *      to all interfaces. Once it hits zero the device reverts back to normal
  *      filtering operation. A negative @inc value is used to drop the counter
  *      when releasing a resource needing all multicasts.
+ *      Return 0 if successful or a negative errno code on error.
  */
 
-void dev_set_allmulti(struct net_device *dev, int inc)
+int dev_set_allmulti(struct net_device *dev, int inc)
 {
         unsigned short old_flags = dev->flags;
 
         ASSERT_RTNL();
 
         dev->flags |= IFF_ALLMULTI;
-        if ((dev->allmulti += inc) == 0)
-                dev->flags &= ~IFF_ALLMULTI;
+        dev->allmulti += inc;
+        if (dev->allmulti == 0) {
+                /*
+                 * Avoid overflow.
+                 * If inc causes overflow, untouch allmulti and return error.
+                 */
+                if (inc < 0)
+                        dev->flags &= ~IFF_ALLMULTI;
+                else {
+                        dev->allmulti -= inc;
+                        printk(KERN_WARNING "%s: allmulti touches roof, "
+                                "set allmulti failed, allmulti feature of "
+                                "device might be broken.\n", dev->name);
+                        return -EOVERFLOW;
+                }
+        }
         if (dev->flags ^ old_flags) {
                 if (dev->change_rx_flags)
                         dev->change_rx_flags(dev, IFF_ALLMULTI);
                 dev_set_rx_mode(dev);
         }
+        return 0;
 }
 
 /*