[PATCH] cfg80211: Fix for crash in cfg80211

[PATCH] cfg80211: Fix for crash in cfg80211

[Srinivasan B]

Patch Description:
                     cfg80211 module crashes when cfg80211 & mac80211 
loaded and unloading lmac driver.

Scenario Explanation:
                     (Step 1) : cfg80211, mac80211 and lmac driver 
modules are loaded initially.
                     (Step 2) : unload the lmac driver.
                                     then any dev calls to stack causes 
the crash.
Code Changes:
                     dev->ethtools_ops is assigned during 
NETDEV_REGISTER and the same can be cleared during NETDEV_UNREGISTER.

Signed-off-by: Srinivasan Chandrasekaran <srinivasb@posedge.com>
---

diff --git a/net/wireless/core.c b/net/wireless/core.c
index dcd64d5..74bb7c4 100755
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -944,6 +944,10 @@ static int cfg80211_netdev_notifier_call(struct 
notifier_block *nb,
  #endif
          }
          mutex_unlock(&rdev->devlist_mtx);
+
+        if (dev->ethtool_ops)
+            dev->ethtool_ops = NULL;
+
          /*
           * synchronise (so that we won't find this netdev
           * from other code any more) and then clear the list

Re: [PATCH] cfg80211: Fix for crash in cfg80211

[Johannes Berg]

On Tue, 2012-08-07 at 12:40 +0530, Srinivasan B wrote:
> Patch Description:
>                      cfg80211 module crashes when cfg80211 & mac80211 
> loaded and unloading lmac driver.
> 
> Scenario Explanation:
>                      (Step 1) : cfg80211, mac80211 and lmac driver 
> modules are loaded initially.
>                      (Step 2) : unload the lmac driver.
>                                      then any dev calls to stack causes 
> the crash.
> Code Changes:
>                      dev->ethtools_ops is assigned during 
> NETDEV_REGISTER and the same can be cleared during NETDEV_UNREGISTER.

This doesn't make any sense to me at all.

johannes

Re: [PATCH] cfg80211: Fix for crash in cfg80211

[Mahesh Palivela]

On 8/7/2012 5:12 PM, Johannes Berg wrote:
> On Tue, 2012-08-07 at 12:40 +0530, Srinivasan B wrote:
>> Patch Description:
>>                       cfg80211 module crashes when cfg80211 & mac80211
>> loaded and unloading lmac driver.
>>
>> Scenario Explanation:
>>                       (Step 1) : cfg80211, mac80211 and lmac driver
>> modules are loaded initially.
>>                       (Step 2) : unload the lmac driver.
>>                                       then any dev calls to stack causes
>> the crash.
>> Code Changes:
>>                       dev->ethtools_ops is assigned during
>> NETDEV_REGISTER and the same can be cleared during NETDEV_UNREGISTER.
>
> This doesn't make any sense to me at all.
>
cleanup of ethtools_ops pointer is required upon netdev_unreg 
notification. we are assigning this pointer to cfg80211_ethtool_ops on 
netdev_reg notification. Is it not required?

we have seen crash when keeping cfg80211 and mac80211 loaded and lmac 
driver unloaded. With this fix, we didn't see crash. Crash doesn't 
happen right away. Only when some operation trying to access ethtool_ops.

> johannes
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: [PATCH] cfg80211: Fix for crash in cfg80211

[Johannes Berg]

On Tue, 2012-08-07 at 18:52 +0530, Mahesh Palivela wrote:

> >>                       dev->ethtools_ops is assigned during
> >> NETDEV_REGISTER and the same can be cleared during NETDEV_UNREGISTER.
> >
> > This doesn't make any sense to me at all.
> >
> cleanup of ethtools_ops pointer is required upon netdev_unreg 
> notification. we are assigning this pointer to cfg80211_ethtool_ops on 
> netdev_reg notification. Is it not required?
> 
> we have seen crash when keeping cfg80211 and mac80211 loaded and lmac 
> driver unloaded. With this fix, we didn't see crash. Crash doesn't 
> happen right away. Only when some operation trying to access ethtool_ops.

I don't see how anything could access ethtool_ops after the netdev is
unregistered.

johannes