net/mlx5e: Check for NOT_READY flag state after locking

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

net/mlx5e: Check for NOT_READY flag state after locking

Currently the check for NOT_READY flag is performed before obtaining the
necessary lock. This opens a possibility for race condition when the flow
is concurrently removed from unready_flows list by the workqueue task,
which causes a double-removal from the list and a crash[0]. Fix the issue
by moving the flag check inside the section protected by
uplink_priv->unready_flows_lock mutex.

[0]:
[44376.389654] general protection fault, probably for non-canonical address 0xdead000000000108: 0000 [#1] SMP
[44376.391665] CPU: 7 PID: 59123 Comm: tc Not tainted 6.4.0-rc4+ #1
[44376.392984] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[44376.395342] RIP: 0010:mlx5e_tc_del_fdb_flow+0xb3/0x340 [mlx5_core]
[44376.396857] Code: 00 48 8b b8 68 ce 02 00 e8 8a 4d 02 00 4c 8d a8 a8 01 00 00 4c 89 ef e8 8b 79 88 e1 48 8b 83 98 06 00 00 48 8b 93 90 06 00 00 <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89 83 90 06
[44376.399167] RSP: 0018:ffff88812cc97570 EFLAGS: 00010246
[44376.399680] RAX: dead000000000122 RBX: ffff8881088e3800 RCX: ffff8881881bac00
[44376.400337] RDX: dead000000000100 RSI: ffff88812cc97500 RDI: ffff8881242f71b0
[44376.401001] RBP: ffff88811cbb0940 R08: 0000000000000400 R09: 0000000000000001
[44376.401663] R10: 0000000000000001 R11: 0000000000000000 R12: ffff88812c944000
[44376.402342] R13: ffff8881242f71a8 R14: ffff8881222b4000 R15: 0000000000000000
[44376.402999] FS: 00007f0451104800(0000) GS:ffff88852cb80000(0000) knlGS:0000000000000000
[44376.403787] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[44376.404343] CR2: 0000000000489108 CR3: 0000000123a79003 CR4: 0000000000370ea0
[44376.405004] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[44376.405665] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[44376.406339] Call Trace:
[44376.406651] <TASK>
[44376.406939] ? die_addr+0x33/0x90
[44376.407311] ? exc_general_protection+0x192/0x390
[44376.407795] ? asm_exc_general_protection+0x22/0x30
[44376.408292] ? mlx5e_tc_del_fdb_flow+0xb3/0x340 [mlx5_core]
[44376.408876] __mlx5e_tc_del_fdb_peer_flow+0xbc/0xe0 [mlx5_core]
[44376.409482] mlx5e_tc_del_flow+0x42/0x210 [mlx5_core]
[44376.410055] mlx5e_flow_put+0x25/0x50 [mlx5_core]
[44376.410529] mlx5e_delete_flower+0x24b/0x350 [mlx5_core]
[44376.411043] tc_setup_cb_reoffload+0x22/0x80
[44376.411462] fl_reoffload+0x261/0x2f0 [cls_flower]
[44376.411907] ? mlx5e_rep_indr_setup_ft_cb+0x160/0x160 [mlx5_core]
[44376.412481] ? mlx5e_rep_indr_setup_ft_cb+0x160/0x160 [mlx5_core]
[44376.413044] tcf_block_playback_offloads+0x76/0x170
[44376.413497] tcf_block_unbind+0x7b/0xd0
[44376.413881] tcf_block_setup+0x17d/0x1c0
[44376.414269] tcf_block_offload_cmd.isra.0+0xf1/0x130
[44376.414725] tcf_block_offload_unbind+0x43/0x70
[44376.415153] __tcf_block_put+0x82/0x150
[44376.415532] ingress_destroy+0x22/0x30 [sch_ingress]
[44376.415986] qdisc_destroy+0x3b/0xd0
[44376.416343] qdisc_graft+0x4d0/0x620
[44376.416706] tc_get_qdisc+0x1c9/0x3b0
[44376.417074] rtnetlink_rcv_msg+0x29c/0x390
[44376.419978] ? rep_movs_alternative+0x3a/0xa0
[44376.420399] ? rtnl_calcit.isra.0+0x120/0x120
[44376.420813] netlink_rcv_skb+0x54/0x100
[44376.421192] netlink_unicast+0x1f6/0x2c0
[44376.421573] netlink_sendmsg+0x232/0x4a0
[44376.421980] sock_sendmsg+0x38/0x60
[44376.422328] ____sys_sendmsg+0x1d0/0x1e0
[44376.422709] ? copy_msghdr_from_user+0x6d/0xa0
[44376.423127] ___sys_sendmsg+0x80/0xc0
[44376.423495] ? ___sys_recvmsg+0x8b/0xc0
[44376.423869] __sys_sendmsg+0x51/0x90
[44376.424226] do_syscall_64+0x3d/0x90
[44376.424587] entry_SYSCALL_64_after_hwframe+0x46/0xb0
[44376.425046] RIP: 0033:0x7f045134f887
[44376.425403] Code: 0a 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b9 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00
---truncated---