CVE-2022-48842 in Linux
Summary
by MITRE • 07/16/2024
In the Linux kernel, the following vulnerability has been resolved:
ice: Fix race condition during interface enslave
Commit 5dbbbd01cbba83 ("ice: Avoid RTNL lock when re-creating auxiliary device") changes a process of re-creation of aux device so ice_plug_aux_dev() is called from ice_service_task() context. This unfortunately opens a race window that can result in dead-lock when interface has left LAG and immediately enters LAG again.
Reproducer: ``` #!/bin/sh
ip link add lag0 type bond mode 1 miimon 100 ip link set lag0
for n in {1..10}; do
echo Cycle: $n ip link set ens7f0 master lag0 sleep 1 ip link set ens7f0 nomaster done ```
This results in: [20976.208697] Workqueue: ice ice_service_task [ice]
[20976.213422] Call Trace:
[20976.215871] __schedule+0x2d1/0x830
[20976.219364] schedule+0x35/0xa0
[20976.222510] schedule_preempt_disabled+0xa/0x10
[20976.227043] __mutex_lock.isra.7+0x310/0x420
[20976.235071] enum_all_gids_of_dev_cb+0x1c/0x100 [ib_core]
[20976.251215] ib_enum_roce_netdev+0xa4/0xe0 [ib_core]
[20976.256192] ib_cache_setup_one+0x33/0xa0 [ib_core]
[20976.261079] ib_register_device+0x40d/0x580 [ib_core]
[20976.266139] irdma_ib_register_device+0x129/0x250 [irdma]
[20976.281409] irdma_probe+0x2c1/0x360 [irdma]
[20976.285691] auxiliary_bus_probe+0x45/0x70
[20976.289790] really_probe+0x1f2/0x480
[20976.298509] driver_probe_device+0x49/0xc0
[20976.302609] bus_for_each_drv+0x79/0xc0
[20976.306448] __device_attach+0xdc/0x160
[20976.310286] bus_probe_device+0x9d/0xb0
[20976.314128] device_add+0x43c/0x890
[20976.321287] __auxiliary_device_add+0x43/0x60
[20976.325644] ice_plug_aux_dev+0xb2/0x100 [ice]
[20976.330109] ice_service_task+0xd0c/0xed0 [ice]
[20976.342591] process_one_work+0x1a7/0x360
[20976.350536] worker_thread+0x30/0x390
[20976.358128] kthread+0x10a/0x120
[20976.365547] ret_from_fork+0x1f/0x40
... [20976.438030] task:ip state:D stack: 0 pid:213658 ppid:213627 flags:0x00004084
[20976.446469] Call Trace:
[20976.448921] __schedule+0x2d1/0x830
[20976.452414] schedule+0x35/0xa0
[20976.455559] schedule_preempt_disabled+0xa/0x10
[20976.460090] __mutex_lock.isra.7+0x310/0x420
[20976.464364] device_del+0x36/0x3c0
[20976.467772] ice_unplug_aux_dev+0x1a/0x40 [ice]
[20976.472313] ice_lag_event_handler+0x2a2/0x520 [ice]
[20976.477288] notifier_call_chain+0x47/0x70
[20976.481386] __netdev_upper_dev_link+0x18b/0x280
[20976.489845] bond_enslave+0xe05/0x1790 [bonding]
[20976.494475] do_setlink+0x336/0xf50
[20976.502517] __rtnl_newlink+0x529/0x8b0
[20976.543441] rtnl_newlink+0x43/0x60
[20976.546934] rtnetlink_rcv_msg+0x2b1/0x360
[20976.559238] netlink_rcv_skb+0x4c/0x120
[20976.563079] netlink_unicast+0x196/0x230
[20976.567005] netlink_sendmsg+0x204/0x3d0
[20976.570930] sock_sendmsg+0x4c/0x50
[20976.574423] ____sys_sendmsg+0x1eb/0x250
[20976.586807] ___sys_sendmsg+0x7c/0xc0
[20976.606353] __sys_sendmsg+0x57/0xa0
[20976.609930] do_syscall_64+0x5b/0x1a0
[20976.613598] entry_SYSCALL_64_after_hwframe+0x65/0xca
1. Command 'ip link ... set nomaster' causes that ice_plug_aux_dev() is called from ice_service_task() context, aux device is created and associated device->lock is taken. 2. Command 'ip link ... set master...' calls ice's notifier under RTNL lock and that notifier calls ice_unplug_aux_dev(). That function tries to take aux device->lock but this is already taken by ice_plug_aux_dev() in step 1 3. Later ice_plug_aux_dev() tries to take RTNL lock but this is already taken in step 2 4. Dead-lock
The patch fixes this issue by following changes: - Bit ICE_FLAG_PLUG_AUX_DEV is kept to be set during ice_plug_aux_dev() call in ice_service_task() - The bit is checked in ice_clear_rdma_cap() and only if it is not set then ice_unplug_aux_dev() is called. If it is set (in other words plugging of aux device was requested and ice_plug_aux_dev() is potentially running) then the function only clears the ---truncated---
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Analysis
by VulDB Data Team • 07/17/2024
The vulnerability described in CVE-2022-48842 resides within the Linux kernel's ice driver, which manages Intel Ethernet network adapters. This flaw manifests as a race condition during the process of interface enslavement into a Link Aggregation Group (LAG), leading to a potential deadlock scenario. The root cause stems from a change introduced in commit 5dbbbd01cbba83, which altered how auxiliary devices are re-created. Specifically, the function ice_plug_aux_dev() began executing within the ice_service_task() context, inadvertently creating a window where concurrent operations could lead to mutual exclusion conflicts.
The technical flaw arises from the interaction between two distinct locking mechanisms: the RTNL (Routing Netlink) lock and the auxiliary device lock. When an interface is removed from a LAG and immediately re-added, the sequence of operations triggers a deadlock. First, the command to remove the interface from the LAG causes ice_plug_aux_dev() to execute in the service task context, taking the auxiliary device's lock. Subsequently, the command to re-add the interface to the LAG invokes the notifier under the RTNL lock, which in turn calls ice_unplug_aux_dev(). This function attempts to acquire the auxiliary device lock that is already held by ice_plug_aux_dev(), while ice_plug_aux_dev() itself tries to acquire the RTNL lock that is currently held by ice_unplug_aux_dev(). This circular dependency results in a system-wide deadlock, halting further network operations.
The operational impact of this vulnerability is significant, particularly in environments where dynamic network reconfiguration is common, such as data centers or high-availability setups. The deadlock can cause complete network service disruption, forcing administrators to manually reboot affected systems or perform kernel updates to resolve the issue. The vulnerability has been classified under CWE-362, which describes a race condition in software where multiple threads or processes access shared resources concurrently, leading to unpredictable behavior or system failures. The ATT&CK framework categorizes this as a privilege escalation technique through system resource exhaustion or manipulation, where an attacker could potentially exploit the deadlock condition to cause denial of service or system instability.
The patch addresses this issue by introducing a flag-based mechanism to prevent the conflicting lock acquisition. The ICE_FLAG_PLUG_AUX_DEV flag ensures that when ice_plug_aux_dev() is executing, ice_clear_rdma_cap() will defer calling ice_unplug_aux_dev() until the plug operation is complete. This design prevents the circular lock dependency by allowing the plug operation to complete before attempting to unplug the device. The solution maintains the intended functionality of auxiliary device management while eliminating the race condition that led to the deadlock. The fix aligns with security best practices by ensuring proper synchronization mechanisms are in place to prevent concurrent access violations in kernel space operations, thereby maintaining system stability and preventing unauthorized access to network resources.