syzbot

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

read to 0xffff8881256f9850 of 8 bytes by task 17374 on cpu 1:
 d_unhashed include/linux/dcache.h:336 [inline]
 __d_lookup_rcu+0x16e/0x3e0 fs/dcache.c:2268
 d_alloc_parallel+0x17f/0xe00 fs/dcache.c:2532
 __lookup_slow+0xb4/0x2a0 fs/namei.c:1648
 lookup_slow+0x4f/0x70 fs/namei.c:1682
 walk_component+0x490/0xd90 fs/namei.c:1802
 link_path_walk.part.0+0x5d3/0xa90 fs/namei.c:2128
 link_path_walk fs/namei.c:2059 [inline]
 path_openat+0x14f/0x3580 fs/namei.c:3536
 do_filp_open+0x11e/0x1b0 fs/namei.c:3567
 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/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881256f9850 of 8 bytes by task 17375 on cpu 0:
 hlist_bl_add_head_rcu include/linux/rculist_bl.h:81 [inline]
 __d_rehash+0x1ba/0x250 fs/dcache.c:2465
 __d_add fs/dcache.c:2659 [inline]
 d_splice_alias+0x325/0x910 fs/dcache.c:3046
 proc_sys_lookup+0x1f6/0x2f0 fs/proc/proc_sysctl.c:566
 __lookup_slow+0x129/0x2a0 fs/namei.c:1665
 lookup_slow+0x4f/0x70 fs/namei.c:1682
 walk_component+0x490/0xd90 fs/namei.c:1802
 link_path_walk.part.0+0x5d3/0xa90 fs/namei.c:2128
 link_path_walk fs/namei.c:2059 [inline]
 path_openat+0x14f/0x3580 fs/namei.c:3536
 do_filp_open+0x11e/0x1b0 fs/namei.c:3567
 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/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 17375 Comm: syz-executor.0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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