syzbot

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BUG: KCSAN: data-race in kcm_rcv_strparser / kcm_rfree

write to 0xffff88811e36f7f8 of 1 bytes by task 9979 on cpu 1:
 reserve_rx_kcm net/kcm/kcmsock.c:282 [inline]
 kcm_rcv_strparser+0x273/0x3d0 net/kcm/kcmsock.c:362
 __strp_recv+0x699/0xf00 net/strparser/strparser.c:309
 strp_recv+0x6d/0x80 net/strparser/strparser.c:343
 tcp_read_sock+0x290/0xb10 net/ipv4/tcp.c:1646
 strp_read_sock net/strparser/strparser.c:366 [inline]
 do_strp_work net/strparser/strparser.c:414 [inline]
 strp_work+0xd9/0x170 net/strparser/strparser.c:423
 process_one_work+0x3cb/0x990 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x210/0x220 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

read to 0xffff88811e36f7f8 of 1 bytes by task 19168 on cpu 0:
 kcm_rfree+0xc6/0x180 net/kcm/kcmsock.c:180
 skb_release_head_state+0xb3/0x170 net/core/skbuff.c:651
 skb_release_all net/core/skbuff.c:662 [inline]
 __kfree_skb+0x14/0x150 net/core/skbuff.c:678
 kfree_skb+0x53/0x190 net/core/skbuff.c:696
 kcm_recvmsg+0x3ae/0x430 net/kcm/kcmsock.c:1160
 ____sys_recvmsg+0x15a/0x2e0 include/linux/uio.h:235
 ___sys_recvmsg net/socket.c:2617 [inline]
 do_recvmmsg+0x35c/0xa30 net/socket.c:2715
 __sys_recvmmsg net/socket.c:2794 [inline]
 __do_sys_recvmmsg net/socket.c:2817 [inline]
 __se_sys_recvmmsg net/socket.c:2810 [inline]
 __x64_sys_recvmmsg+0xcc/0x150 net/socket.c:2810
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19168 Comm: syz-executor.0 Not tainted 5.8.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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