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BUG: KCSAN: data-race in kcm_rcv_strparser / kcm_rfree

write to 0xffff88810712ebb8 of 1 bytes by task 20771 on cpu 0:
 reserve_rx_kcm net/kcm/kcmsock.c:282 [inline]
 kcm_rcv_strparser+0x3a6/0x4d0 net/kcm/kcmsock.c:362
 __strp_recv+0x33e/0xf20 net/strparser/strparser.c:309
 strp_recv+0x77/0x90 net/strparser/strparser.c:343
 tcp_read_sock+0x184/0x690 net/ipv4/tcp.c:1638
 strp_read_sock+0xd8/0x140 net/strparser/strparser.c:366
 do_strp_work net/strparser/strparser.c:414 [inline]
 strp_work+0x90/0xd0 net/strparser/strparser.c:423
 process_one_work+0x424/0x930 kernel/workqueue.c:2264
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2410
 kthread+0x1cb/0x1f0 kernel/kthread.c:255
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff88810712ebb8 of 1 bytes by task 31087 on cpu 1:
 kcm_rfree+0xe7/0x1d0 net/kcm/kcmsock.c:180
 skb_release_head_state+0xb0/0x180 net/core/skbuff.c:653
 skb_release_all+0x1b/0x50 net/core/skbuff.c:664
 __kfree_skb net/core/skbuff.c:680 [inline]
 kfree_skb net/core/skbuff.c:698 [inline]
 kfree_skb+0x93/0x200 net/core/skbuff.c:692
 kcm_recvmsg+0x2d7/0x320 net/kcm/kcmsock.c:1162
 sock_recvmsg_nosec net/socket.c:886 [inline]
 ____sys_recvmsg+0x343/0x350 net/socket.c:2564
 ___sys_recvmsg+0xb2/0x100 net/socket.c:2608
 do_recvmmsg+0x17a/0x540 net/socket.c:2706
 __sys_recvmmsg+0x1f1/0x200 net/socket.c:2785
 __do_sys_recvmmsg net/socket.c:2808 [inline]
 __se_sys_recvmmsg net/socket.c:2801 [inline]
 __x64_sys_recvmmsg+0x82/0xb0 net/socket.c:2801
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 31087 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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