CVE-2026-31508
Description
In the Linux kernel, the following vulnerability has been resolved:
net: openvswitch: Avoid releasing netdev before teardown completes
The patch cited in the Fixes tag below changed the teardown code for OVS ports to no longer unconditionally take the RTNL. After this change, the netdev_destroy() callback can proceed immediately to the call_rcu() invocation if the IFF_OVS_DATAPATH flag is already cleared on the netdev.
The ovs_netdev_detach_dev() function clears the flag before completing the unregistration, and if it gets preempted after clearing the flag (as can happen on an -rt kernel), netdev_destroy() can complete and the device can be freed before the unregistration completes. This leads to a splat like:
[ 998.393867] Oops: general protection fault, probably for non-canonical address 0xff00000001000239: 0000 [#1] SMP PTI [ 998.393877] CPU: 42 UID: 0 PID: 55177 Comm: ip Kdump: loaded Not tainted 6.12.0-211.1.1.el10_2.x86_64+rt #1 PREEMPT_RT [ 998.393886] Hardware name: Dell Inc. PowerEdge R740/0JMK61, BIOS 2.24.0 03/27/2025 [ 998.393889] RIP: 0010:dev_set_promiscuity+0x8d/0xa0 [ 998.393901] Code: 00 00 75 d8 48 8b 53 08 48 83 ba b0 02 00 00 00 75 ca 48 83 c4 08 5b c3 cc cc cc cc 48 83 bf 48 09 00 00 00 75 91 48 8b 47 08 <48> 83 b8 b0 02 00 00 00 74 97 eb 81 0f 1f 80 00 00 00 00 90 90 90 [ 998.393906] RSP: 0018:ffffce5864a5f6a0 EFLAGS: 00010246 [ 998.393912] RAX: ff00000000ffff89 RBX: ffff894d0adf5a05 RCX: 0000000000000000 [ 998.393917] RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff894d0adf5a05 [ 998.393921] RBP: ffff894d19252000 R08: ffff894d19252000 R09: 0000000000000000 [ 998.393924] R10: ffff894d19252000 R11: ffff894d192521b8 R12: 0000000000000006 [ 998.393927] R13: ffffce5864a5f738 R14: 00000000ffffffe2 R15: 0000000000000000 [ 998.393931] FS: 00007fad61971800(0000) GS:ffff894cc0140000(0000) knlGS:0000000000000000 [ 998.393936] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 998.393940] CR2: 000055df0a2a6e40 CR3: 000000011c7fe003 CR4: 00000000007726f0 [ 998.393944] PKRU: 55555554 [ 998.393946] Call Trace: [ 998.393949] <TASK> [ 998.393952] ? show_trace_log_lvl+0x1b0/0x2f0 [ 998.393961] ? show_trace_log_lvl+0x1b0/0x2f0 [ 998.393975] ? dp_device_event+0x41/0x80 [openvswitch] [ 998.394009] ? __die_body.cold+0x8/0x12 [ 998.394016] ? die_addr+0x3c/0x60 [ 998.394027] ? exc_general_protection+0x16d/0x390 [ 998.394042] ? asm_exc_general_protection+0x26/0x30 [ 998.394058] ? dev_set_promiscuity+0x8d/0xa0 [ 998.394066] ? ovs_netdev_detach_dev+0x3a/0x80 [openvswitch] [ 998.394092] dp_device_event+0x41/0x80 [openvswitch] [ 998.394102] notifier_call_chain+0x5a/0xd0 [ 998.394106] unregister_netdevice_many_notify+0x51b/0xa60 [ 998.394110] rtnl_dellink+0x169/0x3e0 [ 998.394121] ? rt_mutex_slowlock.constprop.0+0x95/0xd0 [ 998.394125] rtnetlink_rcv_msg+0x142/0x3f0 [ 998.394128] ? avc_has_perm_noaudit+0x69/0xf0 [ 998.394130] ? __pfx_rtnetlink_rcv_msg+0x10/0x10 [ 998.394132] netlink_rcv_skb+0x50/0x100 [ 998.394138] netlink_unicast+0x292/0x3f0 [ 998.394141] netlink_sendmsg+0x21b/0x470 [ 998.394145] ____sys_sendmsg+0x39d/0x3d0 [ 998.394149] ___sys_sendmsg+0x9a/0xe0 [ 998.394156] __sys_sendmsg+0x7a/0xd0 [ 998.394160] do_syscall_64+0x7f/0x170 [ 998.394162] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 998.394165] RIP: 0033:0x7fad61bf4724 [ 998.394188] Code: 89 02 b8 ff ff ff ff eb bb 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 80 3d c5 e9 0c 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89 [ 998.394189] RSP: 002b:00007ffd7e2f7cb8 EFLAGS: 00000202 ORIG_RAX: 000000000000002e [ 998.394191] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fad61bf4724 [ 998.394193] RDX: 0000000000000000 RSI: 00007ffd7e2f7d20 RDI: 0000000000000003 [ 998.394194] RBP: 00007ffd7e2f7d90 R08: 0000000000000010 R09: 000000000000003f [ 998.394195] R10: 000055df11558010 R11: 0000000000000202 R12: 00007ffd7e2 ---truncated---
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A race condition in Linux kernel's Open vSwitch teardown path can free a netdev before unregistration finishes, leading to a use-after-free crash.
Vulnerability
Overview
A race condition exists in the Linux kernel's Open vSwitch (OVS) module during port teardown. The function ovs_netdev_detach_dev() clears the IFF_OVS_DATAPATH flag on a netdev before completing the unregistration process. A previous patch (referenced in the Fixes tag) changed the teardown code so that it no longer unconditionally takes the RTNL lock. This can allow the netdev_destroy() callback to proceed immediately to a call_rcu() invocation once the flag is cleared, potentially freeing the device before the unregistration has fully completed [1].
Exploitation
Conditions
This race is especially triggerable on kernels with PREEMPT_RT, where preemption after the flag is cleared can lead to the teardown completing prematurely. The attack surface is local; an attacker with the ability to trigger OVS port removal (e.g., by sending netlink commands or removing a port) can cause the race. No special privileges beyond those needed to manage OVS ports are required, as this is a kernel-internal race condition exposed through normal OVS operations.
Impact
If the race is won, the kernel accesses a freed netdev structure, leading to a general protection fault (as shown by the reported splat). This results in a denial-of-service (DoS) condition—typically a kernel crash or system hang. Under certain memory pressure and timing conditions, it might also be possible to trigger a use-after-free that could be exploited for privilege escalation, though the CVE description and references focus on the crash impact.
Mitigation
Status
Patches have been applied to the stable kernel trees, as indicated by the included commit references [1][2][3][4]. Users should update their kernel to a version containing the fix, which ensures proper synchronization by taking the RTNL lock when the IFF_OVS_DATAPATH flag is still set, preventing the premature free.
AI Insight generated on May 18, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
10cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*+ 9 more
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*range: >=5.10.248,<5.10.253
- cpe:2.3:o:linux:linux_kernel:6.19:-:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*
- (no CPE)
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
8- git.kernel.org/stable/c/33609454be4f582e686a4bf13d4482a5ca0f6c4bnvdPatch
- git.kernel.org/stable/c/43579baa17270aa51f93eb09b6e4af6e047b7f6envdPatch
- git.kernel.org/stable/c/4c3e25a7b711a402fcbbbcfbbdf2868ece1ae7c8nvdPatch
- git.kernel.org/stable/c/5fdeaf591a0942772c2d18ff3563697a49ad01c6nvdPatch
- git.kernel.org/stable/c/755a6300afbd743cda4b102f24f343380ec0e0ffnvdPatch
- git.kernel.org/stable/c/7c770dadfda5cbbde6aa3c4363ed513f1d212bf8nvdPatch
- git.kernel.org/stable/c/95265232b49765a4d00f4d028c100bb7185600f4nvdPatch
- git.kernel.org/stable/c/df3c95be76103604e752131d9495a24814915ecenvdPatch
News mentions
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