syzbot

IPVS: ftp: loaded support on port[0] = 21
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BUG: KCSAN: data-race in __d_lookup / __d_rehash

read to 0xffff8881255576d0 of 8 bytes by task 7838 on cpu 1:
 d_unhashed include/linux/dcache.h:336 [inline]
 __d_lookup+0x152/0x3f0 fs/dcache.c:2375
 lookup_fast+0x26c/0x700 fs/namei.c:1609
 walk_component+0x6d/0xe70 fs/namei.c:1796
 link_path_walk.part.0+0x5d3/0xa90 fs/namei.c:2131
 link_path_walk fs/namei.c:2062 [inline]
 path_openat+0x14f/0x36e0 fs/namei.c:3524
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881255576d0 of 8 bytes by task 7855 on cpu 0:
 hlist_bl_add_head_rcu include/linux/rculist_bl.h:109 [inline]
 __d_rehash+0x1ba/0x250 fs/dcache.c:2463
 __d_add fs/dcache.c:2657 [inline]
 d_splice_alias+0x325/0x910 fs/dcache.c:3044
 proc_sys_lookup+0x1f6/0x2f0 fs/proc/proc_sysctl.c:566
 __lookup_slow+0x129/0x2a0 fs/namei.c:1663
 lookup_slow+0x4f/0x70 fs/namei.c:1680
 walk_component+0x4a2/0xe70 fs/namei.c:1800
 link_path_walk.part.0+0x5d3/0xa90 fs/namei.c:2131
 link_path_walk fs/namei.c:2062 [inline]
 path_openat+0x14f/0x36e0 fs/namei.c:3524
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7855 Comm: syz-executor.2 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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