CVE-2025-23163 net: vlan: don't propagate flags on open
A deadlock in the Linux kernel VLAN subsystem can cause a system hang when opening network devices, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-23163?
CVE-2025-23163 is a medium-severity vulnerability in Debian Debian Linux, published on 1 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: vlan: don't propagate flags on open
With the device instance lock, there is now a possibility of a deadlock:
[ 1.211455] ============================================ [ 1.211571] WARNING: possible recursive locking detected [ 1.211687] 6.14.0-rc5-01215-g032756b4ca7a-dirty #5 Not tainted [ 1.211823] -------------------------------------------- [ 1.211936] ip/184 is trying to acquire lock: [ 1.212032] ffff8881024a4c30 (&dev->lock){+.+.}-{4:4}, at: dev_set_allmulti+0x4e/0xb0 [ 1.212207] [ 1.212207] but task is already holding lock: [ 1.212332] ffff8881024a4c30 (&dev->lock){+.+.}-{4:4}, at: dev_open+0x50/0xb0 [ 1.212487] [ 1.212487] other info that might help us debug this: [ 1.212626] Possible unsafe locking scenario: [ 1.212626] [ 1.212751] CPU0 [ 1.212815] ---- [ 1.212871] lock(&dev->lock); [ 1.212944] lock(&dev->lock); [ 1.213016] [ 1.213016] *** DEADLOCK *** [ 1.213016] [ 1.213143] May be due to missing lock nesting notation [ 1.213143] [ 1.213294] 3 locks held by ip/184: [ 1.213371] #0: ffffffff838b53e0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock+0x1b/0xa0 [ 1.213543] #1: ffffffff84e5fc70 (&net->rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock+0x37/0xa0 [ 1.213727] #2: ffff8881024a4c30 (&dev->lock){+.+.}-{4:4}, at: dev_open+0x50/0xb0 [ 1.213895] [ 1.213895] stack backtrace: [ 1.213991] CPU: 0 UID: 0 PID: 184 Comm: ip Not tainted 6.14.0-rc5-01215-g032756b4ca7a-dirty #5 [ 1.213993] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014 [ 1.213994] Call Trace: [ 1.213995] <TASK> [ 1.213996] dump_stack_lvl+0x8e/0xd0 [ 1.214000] print_deadlock_bug+0x28b/0x2a0 [ 1.214020] lock_acquire+0xea/0x2a0 [ 1.214027] __mutex_lock+0xbf/0xd40 [ 1.214038] dev_set_allmulti+0x4e/0xb0 # real_dev->flags & IFF_ALLMULTI [ 1.214040] vlan_dev_open+0xa5/0x170 # ndo_open on vlandev [ 1.214042] __dev_open+0x145/0x270 [ 1.214046] __dev_change_flags+0xb0/0x1e0 [ 1.214051] netif_change_flags+0x22/0x60 # IFF_UP vlandev [ 1.214053] dev_change_flags+0x61/0xb0 # for each device in group from dev->vlan_info [ 1.214055] vlan_device_event+0x766/0x7c0 # on netdevsim0 [ 1.214058] notifier_call_chain+0x78/0x120 [ 1.214062] netif_open+0x6d/0x90 [ 1.214064] dev_open+0x5b/0xb0 # locks netdevsim0 [ 1.214066] bond_enslave+0x64c/0x1230 [ 1.214075] do_set_master+0x175/0x1e0 # on netdevsim0 [ 1.214077] do_setlink+0x516/0x13b0 [ 1.214094] rtnl_newlink+0xaba/0xb80 [ 1.214132] rtnetlink_rcv_msg+0x440/0x490 [ 1.214144] netlink_rcv_skb+0xeb/0x120 [ 1.214150] netlink_unicast+0x1f9/0x320 [ 1.214153] netlink_sendmsg+0x346/0x3f0 [ 1.214157] __sock_sendmsg+0x86/0xb0 [ 1.214160] ____sys_sendmsg+0x1c8/0x220 [ 1.214164] ___sys_sendmsg+0x28f/0x2d0 [ 1.214179] __x64_sys_sendmsg+0xef/0x140 [ 1.214184] do_syscall_64+0xec/0x1d0 [ 1.214190] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 1.214191] RIP: 0033:0x7f2d1b4a7e56
Device setup:
netdevsim0 (down) ^ ^ bond netdevsim1.100@netdevsim1 allmulticast=on (down)
When we enslave the lower device (netdevsim0) which has a vlan, we propagate vlan's allmuti/promisc flags during ndo_open. This causes (re)locking on of the real_dev.
Propagate allmulti/promisc on flags change, not on the open. There is a slight semantics change that vlans that are down now propagate the flags, but this seems unlikely to result in the real issues.
Reproducer:
echo 0 1 > /sys/bus/netdevsim/new_device
dev_path=$(ls -d /sys/bus/netdevsim/devices/netdevsim0/net/*) dev=$(echo $dev_path | rev | cut -d/ -f1 | rev)
ip link set dev $dev name netdevsim0 ip link set dev netdevsim0 up
ip link add link netdevsim0 name netdevsim0.100 type vlan id 100 ip link set dev netdevsim0.100 allm ---truncated---
Weakness: CWE-667
Which versions are affected by CVE-2025-23163?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-23163?
Apply the vendor's patch.
Is CVE-2025-23163 being exploited?
There is no known exploitation of CVE-2025-23163 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as BELL-CVE-2025-23163, DEBIAN-CVE-2025-23163, GHSA-pj73-39g5-xmf7, ROOT-OS-DEBIAN-12-CVE-2025-23163, ROOT-OS-UBUNTU-2204-CVE-2025-23163, ROOT-OS-UBUNTU-2404-CVE-2025-23163 and 1 more.