Patch "net: vlan: fix a UAF in vlan_dev_real_dev()" has been added to the 4.14-stable tree

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This is a note to let you know that I've just added the patch titled

    net: vlan: fix a UAF in vlan_dev_real_dev()

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-vlan-fix-a-uaf-in-vlan_dev_real_dev.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4280cba2bad7b6ac69cb13a85a9c752b9588dbfa
Author: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
Date:   Tue Nov 2 10:12:18 2021 +0800

    net: vlan: fix a UAF in vlan_dev_real_dev()
    
    [ Upstream commit 563bcbae3ba233c275c244bfce2efe12938f5363 ]
    
    The real_dev of a vlan net_device may be freed after
    unregister_vlan_dev(). Access the real_dev continually by
    vlan_dev_real_dev() will trigger the UAF problem for the
    real_dev like following:
    
    ==================================================================
    BUG: KASAN: use-after-free in vlan_dev_real_dev+0xf9/0x120
    Call Trace:
     kasan_report.cold+0x83/0xdf
     vlan_dev_real_dev+0xf9/0x120
     is_eth_port_of_netdev_filter.part.0+0xb1/0x2c0
     is_eth_port_of_netdev_filter+0x28/0x40
     ib_enum_roce_netdev+0x1a3/0x300
     ib_enum_all_roce_netdevs+0xc7/0x140
     netdevice_event_work_handler+0x9d/0x210
    ...
    
    Freed by task 9288:
     kasan_save_stack+0x1b/0x40
     kasan_set_track+0x1c/0x30
     kasan_set_free_info+0x20/0x30
     __kasan_slab_free+0xfc/0x130
     slab_free_freelist_hook+0xdd/0x240
     kfree+0xe4/0x690
     kvfree+0x42/0x50
     device_release+0x9f/0x240
     kobject_put+0x1c8/0x530
     put_device+0x1b/0x30
     free_netdev+0x370/0x540
     ppp_destroy_interface+0x313/0x3d0
    ...
    
    Move the put_device(real_dev) to vlan_dev_free(). Ensure
    real_dev not be freed before vlan_dev unregistered.
    
    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Reported-by: syzbot+e4df4e1389e28972e955@xxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
    Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 0efdf83f78e7a..a8cee80e07a70 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -112,9 +112,6 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
 	}
 
 	vlan_vid_del(real_dev, vlan->vlan_proto, vlan_id);
-
-	/* Get rid of the vlan's reference to real_dev */
-	dev_put(real_dev);
 }
 
 int vlan_check_real_dev(struct net_device *real_dev,
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index ed3717dc2d201..d28c22e59996c 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -814,6 +814,9 @@ static void vlan_dev_free(struct net_device *dev)
 
 	free_percpu(vlan->vlan_pcpu_stats);
 	vlan->vlan_pcpu_stats = NULL;
+
+	/* Get rid of the vlan's reference to real_dev */
+	dev_put(vlan->real_dev);
 }
 
 void vlan_setup(struct net_device *dev)



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