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BUG: KCSAN: data-race in kcm_rcv_strparser / kcm_rfree

read to 0xffff8880afe08760 of 8 bytes by task 5737 on cpu 1:
 kcm_rfree+0x11e/0x1e0 net/kcm/kcmsock.c:180
 skb_release_head_state+0xb8/0x180 net/core/skbuff.c:652
 skb_release_all+0x1f/0x60 net/core/skbuff.c:663
 __kfree_skb net/core/skbuff.c:679 [inline]
 kfree_skb net/core/skbuff.c:697 [inline]
 kfree_skb+0x98/0x1d0 net/core/skbuff.c:691
 kcm_recvmsg+0x2d1/0x320 net/kcm/kcmsock.c:1162
 sock_recvmsg_nosec+0x5c/0x70 net/socket.c:871
 ___sys_recvmsg+0x1a0/0x3e0 net/socket.c:2480
 do_recvmmsg+0x19a/0x5c0 net/socket.c:2601
 __sys_recvmmsg+0x1ef/0x200 net/socket.c:2680
 __do_sys_recvmmsg net/socket.c:2703 [inline]
 __se_sys_recvmmsg net/socket.c:2696 [inline]
 __x64_sys_recvmmsg+0x89/0xb0 net/socket.c:2696
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880afe08760 of 8 bytes by task 7858 on cpu 0:
 reserve_rx_kcm net/kcm/kcmsock.c:285 [inline]
 kcm_rcv_strparser+0x3ac/0x4c0 net/kcm/kcmsock.c:362
 __strp_recv+0x348/0xf50 net/strparser/strparser.c:309
 strp_recv+0x84/0xa0 net/strparser/strparser.c:343
 tcp_read_sock+0x174/0x640 net/ipv4/tcp.c:1641
 strp_read_sock+0xd4/0x140 net/strparser/strparser.c:366
 do_strp_work net/strparser/strparser.c:414 [inline]
 strp_work+0x9a/0xe0 net/strparser/strparser.c:423
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7858 Comm: kworker/u4:4 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kstrp strp_work
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