In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: TC, Check if flow is PEER before acquiring devcom lock In c

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5e: TC, Check if flow is PEER before acquiring devcom lock

In case __mlx5e_add_fdb_flow() fails in lower levels, the flow is
deleted via mlx5e_tc_del_flow(), and mlx5e_tc_del_flow() is acquiring
ESW devcom lock without condition. In addition, in case of peer_flow,
__mlx5e_add_fdb_flow() is called while holding ESW devcom comp lock.
This results in an AA deadlock.

To fix this, introduce a new PEER flag that is set on flows created as
peer flows (the duplicate flows on peer devices), and check it in
mlx5e_tc_del_flow() before acquiring ESW devcom lock.

Lockdep splat:

WARNING: possible recursive locking detected

Possible unsafe locking scenario:
CPU0
----
lock(&comp->lock_key#2);
lock(&comp->lock_key#2);
*** DEADLOCK ***
Call Trace:
<TASK>
dump_stack_lvl+0x69/0xa0
print_deadlock_bug.cold+0xbd/0xca
__lock_acquire+0x1671/0x2ec0
lock_acquire+0x10e/0x2e0
down_read+0x95/0x430
mlx5_devcom_for_each_peer_begin+0x4e/0xe0 [mlx5_core]
mlx5e_tc_del_flow+0x11d/0xa70 [mlx5_core]
mlx5e_flow_put+0x99/0x100 [mlx5_core]
__mlx5e_add_fdb_flow+0x409/0xf00 [mlx5_core]
mlx5e_configure_flower+0x2a86/0x4100 [mlx5_core]
mlx5e_rep_setup_tc_cls_flower+0x12f/0x1b0 [mlx5_core]
mlx5e_rep_setup_tc_cb+0x153/0x750 [mlx5_core]
tc_setup_cb_add+0x1dc/0x470
fl_change+0x2f4d/0x626d [cls_flower]
tc_new_tfilter+0x79b/0x2310
rtnetlink_rcv_msg+0x778/0xad0
do_syscall_64+0x70/0x960
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>