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BUG: KCSAN: data-race in prandom_seed / prandom_u32

write to 0xffff888237d28858 of 8 bytes by task 4860 on cpu 1:
 siprand_u32 lib/random32.c:372 [inline]
 prandom_u32+0x12f/0x190 lib/random32.c:387
 fat_fill_inode+0xf5/0xa00 fs/fat/inode.c:526
 fat_build_inode+0x1c7/0x2a0 fs/fat/inode.c:609
 msdos_create+0x257/0x2d0 fs/fat/namei_msdos.c:292
 lookup_open fs/namei.c:3330 [inline]
 open_last_lookups fs/namei.c:3400 [inline]
 path_openat+0xc50/0x1b30 fs/namei.c:3606
 do_filp_open+0x105/0x220 fs/namei.c:3636
 do_sys_openat2+0xb5/0x2a0 fs/open.c:1213
 do_sys_open fs/open.c:1229 [inline]
 __do_sys_creat fs/open.c:1305 [inline]
 __se_sys_creat fs/open.c:1299 [inline]
 __x64_sys_creat+0x62/0x80 fs/open.c:1299
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237d28858 of 8 bytes by task 1863 on cpu 0:
 prandom_seed+0xeb/0x270 lib/random32.c:440
 addrconf_dad_begin net/ipv6/addrconf.c:3975 [inline]
 addrconf_dad_work+0x265/0xbb0 net/ipv6/addrconf.c:4100
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0xfe534e6c235694c9 -> 0x5b500231867cd466

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1863 Comm: kworker/0:2 Not tainted 5.18.0-rc7-syzkaller-00015-gef1302160bfb-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ipv6_addrconf addrconf_dad_work
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