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Message-ID: <48586A04.6040800@cn.fujitsu.com>
Date: Wed, 18 Jun 2008 09:51:00 +0800
From: Wang Chen <wangchen@...fujitsu.com>
To: Patrick McHardy <kaber@...sh.net>
CC: "David S. Miller" <davem@...emloft.net>,
NETDEV <netdev@...r.kernel.org>
Subject: Re: v2: [PATCH 2/3] netdevice: Fix promiscuity and allmulti overflow
Patrick McHardy said the following on 2008-6-17 20:59:
>> + printk(KERN_ERR "%s: promiscuity touches roof, "
>> + "set promiscuity failed, promiscuity feature "
>> + "of device will be broken.\n", dev->name);
>> + return -EOVERFLOW;
>> + }
>> + }
>
> Assuming the caller does proper error handling, that printk is
> not true.
>
Yes.
But currently, no caller handling this, and I think even if I make
some callers to handle this, but there maybe some callers and their
callers do not want to handle error condition.
So I need a KERN_WARNING here.
If some day, all of the caller handle the error properly, we can
remove this printk.
Here is v3:
---
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@...fujitsu.com>
---
include/linux/netdevice.h | 4 +-
net/core/dev.c | 55 ++++++++++++++++++++++++++++++++++++--------
2 files changed, 47 insertions(+), 12 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f27fd20..f2ab98e 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1476,8 +1476,8 @@ extern int __dev_addr_delete(struct dev_addr_list **list, int *count, void *ad
extern int __dev_addr_add(struct dev_addr_list **list, int *count, void *addr, int alen, int newonly);
extern int __dev_addr_sync(struct dev_addr_list **to, int *to_count, struct dev_addr_list **from, int *from_count);
extern void __dev_addr_unsync(struct dev_addr_list **to, int *to_count, struct dev_addr_list **from, int *from_count);
-extern void dev_set_promiscuity(struct net_device *dev, int inc);
-extern void dev_set_allmulti(struct net_device *dev, int inc);
+extern int dev_set_promiscuity(struct net_device *dev, int inc);
+extern int dev_set_allmulti(struct net_device *dev, int inc);
extern void netdev_state_change(struct net_device *dev);
extern void netdev_features_change(struct net_device *dev);
/* Load a device via the kmod */
diff --git a/net/core/dev.c b/net/core/dev.c
index 5829630..61beb4d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2747,16 +2747,29 @@ 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" :
@@ -2774,6 +2787,7 @@ 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;
}
/**
@@ -2785,14 +2799,19 @@ 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;
}
/**
@@ -2805,22 +2824,38 @@ 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;
}
/*
--
1.5.3.4
--
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