CVE-2024-38557 net/mlx5: Reload only IB representors upon lag disable/enable
A race condition in the mlx5 driver causes a deadlock during LAG disable/enable, leading to a 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-2024-38557?
CVE-2024-38557 is a medium-severity vulnerability in Linux kernel, published on 19 Jun 2024. 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/mlx5: Reload only IB representors upon lag disable/enable
On lag disable, the bond IB device along with all of its representors are destroyed, and then the slaves' representors get reloaded.
In case the slave IB representor load fails, the eswitch error flow unloads all representors, including ethernet representors, where the netdevs get detached and removed from lag bond. Such flow is inaccurate as the lag driver is not responsible for loading/unloading ethernet representors. Furthermore, the flow described above begins by holding lag lock to prevent bond changes during disable flow. However, when reaching the ethernet representors detachment from lag, the lag lock is required again, triggering the following deadlock:
Call trace: __switch_to+0xf4/0x148 __schedule+0x2c8/0x7d0 schedule+0x50/0xe0 schedule_preempt_disabled+0x18/0x28 __mutex_lock.isra.13+0x2b8/0x570 __mutex_lock_slowpath+0x1c/0x28 mutex_lock+0x4c/0x68 mlx5_lag_remove_netdev+0x3c/0x1a0 [mlx5_core] mlx5e_uplink_rep_disable+0x70/0xa0 [mlx5_core] mlx5e_detach_netdev+0x6c/0xb0 [mlx5_core] mlx5e_netdev_change_profile+0x44/0x138 [mlx5_core] mlx5e_netdev_attach_nic_profile+0x28/0x38 [mlx5_core] mlx5e_vport_rep_unload+0x184/0x1b8 [mlx5_core] mlx5_esw_offloads_rep_load+0xd8/0xe0 [mlx5_core] mlx5_eswitch_reload_reps+0x74/0xd0 [mlx5_core] mlx5_disable_lag+0x130/0x138 [mlx5_core] mlx5_lag_disable_change+0x6c/0x70 [mlx5_core] // hold ldev->lock mlx5_devlink_eswitch_mode_set+0xc0/0x410 [mlx5_core] devlink_nl_cmd_eswitch_set_doit+0xdc/0x180 genl_family_rcv_msg_doit.isra.17+0xe8/0x138 genl_rcv_msg+0xe4/0x220 netlink_rcv_skb+0x44/0x108 genl_rcv+0x40/0x58 netlink_unicast+0x198/0x268 netlink_sendmsg+0x1d4/0x418 sock_sendmsg+0x54/0x60 __sys_sendto+0xf4/0x120 __arm64_sys_sendto+0x30/0x40 el0_svc_common+0x8c/0x120 do_el0_svc+0x30/0xa0 el0_svc+0x20/0x30 el0_sync_handler+0x90/0xb8 el0_sync+0x160/0x180
Thus, upon lag enable/disable, load and unload only the IB representors of the slaves preventing the deadlock mentioned above.
While at it, refactor the mlx5_esw_offloads_rep_load() function to have a static helper method for its internal logic, in symmetry with the representor unload design.
Weakness: CWE-667
Which versions are affected by CVE-2024-38557?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-38557?
Apply the vendor's patch.
Is CVE-2024-38557 being exploited?
There is no known exploitation of CVE-2024-38557 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-48307, BELL-CVE-2024-38557, DEBIAN-CVE-2024-38557, GHSA-wp7p-m23w-r9gj, ROOT-OS-DEBIAN-12-CVE-2024-38557, ROOT-OS-UBUNTU-2204-CVE-2024-38557 and 1 more.