linux-kernel - Re: [PATCH] Fix race condition about network device name allocation

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Date:	Wed, 13 Jun 2007 21:36:30 -0700
From:	Jay Vosburgh <fubar@...ibm.com>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
cc:	Dan Aloni <da-x@...atomic.org>,
	Chad Tindel <ctindel@...rs.sourceforge.net>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	bonding-devel@...ts.sourceforge.net
Subject: Re: [PATCH] Fix race condition about network device name allocation 


	The following patch (based on a patch from Stephen Hemminger
<shemminger@...ux-foundation.org>) removes use after free conditions in
the unregister path for the bonding master.  Without this patch, an
operation of the form "echo -bond0 > /sys/class/net/bonding_masters"
would trigger a NULL pointer dereference in sysfs.  I was not able to
induce the failure with the non-sysfs code path, but for consistency I
updated that code as well.

	I also did some testing of the bonding /proc file being open
while the bond is being deleted, and didn't see any problems there.

Signed-off-by: Jay Vosburgh <fubar@...ibm.com>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 223517d..6287ffb 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4345,8 +4345,8 @@ static void bond_free_all(void)
 		bond_mc_list_destroy(bond);
 		/* Release the bonded slaves */
 		bond_release_all(bond_dev);
-		unregister_netdevice(bond_dev);
 		bond_deinit(bond_dev);
+		unregister_netdevice(bond_dev);
 	}
 
 #ifdef CONFIG_PROC_FS
diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index a122baa..60cccf2 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -164,9 +164,9 @@ static ssize_t bonding_store_bonds(struct class *cls, const char *buffer, size_t
 				printk(KERN_INFO DRV_NAME
 					": %s is being deleted...\n",
 					bond->dev->name);
-				unregister_netdevice(bond->dev);
 				bond_deinit(bond->dev);
 		        	bond_destroy_sysfs_entry(bond);
+				unregister_netdevice(bond->dev);
 				rtnl_unlock();
 				goto out;
 			}
-
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