linux-kernel - KCSAN reports several races at boot in timekeeping_get_ns, set_nlink, kernfs_refresh_inode, kernfs_refresh_inode (kernel 6.4-rc4, KCSAN

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Date:   Fri, 2 Jun 2023 01:44:02 +0200
From:   Erhard Furtner <erhard_f@...lbox.org>
To:     linux-kernel@...r.kernel.org
Subject: KCSAN reports several races at boot in timekeeping_get_ns,
 set_nlink, kernfs_refresh_inode, kernfs_refresh_inode (kernel 6.4-rc4,
 KCSAN_STRICT)

Greetings!

As there are several data races in different subsystems I am reporting here as linux-kernel@...r.kernel.org is listed for LKMM in MAINTAINERS. If more appropriate please add specific maintainers.

I get these races on every boot with KCSAN selected until I reach desktop, e.g:

==================================================================
BUG: KCSAN: data-race in set_nlink / set_nlink

read to 0xffff90d50fc177c0 of 4 bytes by task 716 on cpu 1:
 set_nlink+0x25/0x80
 kernfs_refresh_inode+0xf4/0x110
 kernfs_iop_permission+0x71/0xb0
 inode_permission+0x10c/0x1e0
 link_path_walk+0x191/0x5b0
 path_openat+0x14a/0x12b0
 do_filp_open+0xdc/0x140
 do_sys_openat2+0x90/0x200
 do_sys_open+0x6b/0x90
 __x64_sys_openat+0x58/0x80
 do_syscall_64+0x62/0xa0
 entry_SYSCALL_64_after_hwframe+0x4b/0xb5

write to 0xffff90d50fc177c0 of 4 bytes by task 727 on cpu 4:
 set_nlink+0x5e/0x80
 kernfs_refresh_inode+0xf4/0x110
 kernfs_iop_permission+0x71/0xb0
 inode_permission+0x10c/0x1e0
 link_path_walk+0x191/0x5b0
 path_lookupat+0x61/0x1d0
 filename_lookup+0xf3/0x170
 user_path_at_empty+0x43/0x70
 do_faccessat+0x2ac/0x440
 __x64_sys_faccessat+0x44/0x60
 do_syscall_64+0x62/0xa0
 entry_SYSCALL_64_after_hwframe+0x4b/0xb5

Reported by Kernel Concurrency Sanitizer on:
CPU: 4 PID: 727 Comm: (udev-worker) Not tainted 6.4.0-rc4-bdver2 #5
Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./970-GAMING, BIOS F2 04/06/2016
==================================================================

Some reliably happen more often than others:

 $ grep KCSAN dmesg_64-rc4_bdver2 
[    0.012086] BUG: KCSAN: data-race in wq_watchdog_touch / wq_watchdog_touch
[    8.285432] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[    8.368764] BUG: KCSAN: data-race in wq_watchdog_touch / wq_watchdog_touch
[    9.538829] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   11.867629] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   14.723475] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   16.431943] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   20.633945] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   20.908824] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   24.004984] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   25.913675] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   29.478839] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   30.315492] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   30.349322] BUG: KCSAN: data-race in kernfs_refresh_inode / kernfs_refresh_inode
[   32.476264] BUG: KCSAN: data-race in set_nlink / set_nlink
[   32.725498] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   33.093884] BUG: KCSAN: data-race in d_alloc_parallel / d_alloc_parallel
[   33.632176] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   33.772667] BUG: KCSAN: data-race in generic_permission / kernfs_refresh_inode
[   35.844855] BUG: KCSAN: data-race in kernfs_refresh_inode / kernfs_refresh_inode
[   36.098850] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   36.490808] BUG: KCSAN: data-race in generic_fillattr / kernfs_refresh_inode
[   36.532227] BUG: KCSAN: data-race in __hrtimer_run_queues / hrtimer_active
[   36.612581] BUG: KCSAN: data-race in set_nlink / set_nlink
[   36.629559] BUG: KCSAN: data-race in generic_fillattr / set_nlink
[   36.688606] BUG: KCSAN: data-race in __fput / kernfs_refresh_inode
[   47.528845] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   48.885486] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   52.818843] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   56.355483] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   57.018848] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   60.652186] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   63.688828] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   64.185511] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   66.775499] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   71.638848] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   74.808910] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   75.172163] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   78.105499] BUG: KCSAN: data-race in timekeeping_get_ns+0x138/0x1d0
[   78.635498] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   79.302043] BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked
[   82.015496] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   89.365427] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0
[   89.388778] BUG: KCSAN: data-race in __hrtimer_run_queues / hrtimer_active
[   89.403648] BUG: KCSAN: data-race in tick_nohz_idle_got_tick / tick_nohz_stop_idle
[   94.855379] BUG: KCSAN: data-race in timekeeping_get_ns+0x148/0x1d0

Some data about the system:

# inxi -bZ
System:
  Kernel: 6.3.5-gentoo-bdver2 arch: x86_64 bits: 64
    Desktop: MATE v: 1.26.0 Distro: Gentoo Base System release 2.13
Machine:
  Type: Desktop Mobo: Gigabyte model: 970-GAMING v: x.x serial: N/A
    UEFI: American Megatrends v: F2 date: 04/06/2016
CPU:
  Info: 8-core AMD FX-8370 [MT MCP] speed (MHz): avg: 1400 min/max: 1400/4000
Graphics:
  Device-1: AMD Turks XT [Radeon HD 6670/7670] driver: radeon v: kernel
  Display: x11 server: X.Org v: 21.1.8 driver: X: loaded: modesetting
    unloaded: fbdev,radeon gpu: radeon resolution: 1920x1080~60Hz
  OpenGL: renderer: AMD TURKS (DRM 2.50.0 / 6.3.5-gentoo-bdver2 LLVM
    15.0.7) v: 4.5 Mesa 23.1.1
Network:
  Device-1: Qualcomm Atheros Killer E2400 Gigabit Ethernet driver: alx

Kernel dmesg and .config attached.

Regards,
Erhard F.

Download attachment "config_64-rc4_bdver2" of type "application/octet-stream" (126202 bytes)

Download attachment "dmesg_64-rc4_bdver2" of type "application/octet-stream" (129226 bytes)