Subject: CVE-2024-38557: net/mlx5: Reload only IB representors upon lag disable/enable

From: Greg Kroah-Hartman <[email-masked]>

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.

The Linux kernel CVE team has assigned CVE-2024-38557 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.15 with commit 598fe77df855 and fixed in 6.6.33 with commit e93fc8d959e5
	Issue introduced in 5.15 with commit 598fe77df855 and fixed in 6.8.12 with commit f03c714a0fdd
	Issue introduced in 5.15 with commit 598fe77df855 and fixed in 6.9.3 with commit 0f320f28f54b
	Issue introduced in 5.15 with commit 598fe77df855 and fixed in 6.10 with commit 0f06228d4a2d

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-38557
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/net/ethernet/mellanox/mlx5/core/eswitch.h
	drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
	drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c
	drivers/net/ethernet/mellanox/mlx5/core/lag/mpesw.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e93fc8d959e56092e2eca1e5511c2d2f0ad6807a
	https://git.kernel.org/stable/c/f03c714a0fdd1f93101a929d0e727c28a66383fc
	https://git.kernel.org/stable/c/0f320f28f54b1b269a755be2e3fb3695e0b80b07
	https://git.kernel.org/stable/c/0f06228d4a2dcc1fca5b3ddb0eefa09c05b102c4