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 4.19-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-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 571472b0b82812d0b6d862e400b1002023fbd2bd 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 512ada90657b2..64ad86419b08d 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 84ef837721141..52428d9c93b06 100644 --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -816,6 +816,9 @@ 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)