KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (10)

Status: moderation: reported on 2026/08/25 03:54
Subsystems: ext4
Labels: race:benign
[Documentation on labels]
Reported-by: syzbot+7528a49543144ca596b7@syzkaller.appspotmail.com
First crash: 1d14h, last: 1d14h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
e83f8aa9 assessment-kcsan Benign: ✅ KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (10) 2026/08/25 03:54 2026/08/25 03:54 2026/08/25 04:26 23caa175
Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (4) ext4 6 80 848d 993d 0/29 auto-obsoleted due to no activity on 2024/06/03 21:44
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (8) ext4 6 9 265d 437d 0/29 auto-obsoleted due to no activity on 2026/01/28 21:28
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (3) fs 6 1 1285d 1285d 0/29 auto-obsoleted due to no activity on 2023/04/01 03:15
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (5) ext4 6 13 675d 791d 0/29 auto-obsoleted due to no activity on 2024/11/24 11:50
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru fs 6 14 2393d 2460d 0/29 auto-closed as invalid on 2020/04/15 20:03
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (2) ext4 exfat 6 213 1329d 1790d 0/29 auto-obsoleted due to no activity on 2023/02/08 20:39
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (6) ext4 6 1 636d 636d 0/29 auto-obsoleted due to no activity on 2025/01/22 20:51
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (7) ext4 6 6 498d 572d 0/29 auto-obsoleted due to no activity on 2025/06/09 21:46
upstream KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (9) prio:high ext4 6 6 77d 195d 0/29 auto-obsoleted due to no activity on 2026/08/05 13:03

Sample crash report:
loop2: detected capacity change from 0 to 164
==================================================================
BUG: KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru

write to 0xffff888237c277e0 of 8 bytes by task 23926 on cpu 0:
 __invalidate_bh_lrus fs/buffer.c:1414 [inline]
 invalidate_bh_lru+0x8a/0xf0 fs/buffer.c:1426
 csd_do_func kernel/smp.c:143 [inline]
 smp_call_function_many_cond+0x72e/0xbc0 kernel/smp.c:983
 on_each_cpu_cond_mask+0x35/0x50 kernel/smp.c:1169
 on_each_cpu_cond include/linux/smp.h:105 [inline]
 invalidate_bh_lrus+0x2a/0x30 fs/buffer.c:1445
 invalidate_bdev+0x42/0x70 block/bdev.c:99
 ext4_put_super+0x620/0x7c0 fs/ext4/super.c:1357
 generic_shutdown_super+0xee/0x220 fs/super.c:769
 kill_block_super+0x2d/0xb0 fs/super.c:1918
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7527
 deactivate_locked_super+0x75/0x200 fs/super.c:603
 deactivate_super+0x9a/0xb0 fs/super.c:632
 cleanup_mnt+0x2c3/0x340 fs/namespace.c:1317
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1324
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x1e4/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x212/0x360 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237c277e0 of 8 bytes by task 25035 on cpu 1:
 has_bh_in_lru+0x35/0x1f0 fs/buffer.c:1436
 smp_call_function_many_cond+0x2d1/0xbc0 kernel/smp.c:936
 on_each_cpu_cond_mask+0x35/0x50 kernel/smp.c:1169
 on_each_cpu_cond include/linux/smp.h:105 [inline]
 invalidate_bh_lrus+0x2a/0x30 fs/buffer.c:1445
 kill_bdev block/bdev.c:89 [inline]
 set_blocksize+0x1e3/0x270 block/bdev.c:206
 sb_set_blocksize+0x93/0x170 block/bdev.c:239
 sb_min_blocksize+0x53/0x60 block/bdev.c:254
 isofs_fill_super+0x100/0x1340 fs/isofs/inode.c:612
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1887
 get_tree_bdev+0x1f/0x30 fs/super.c:1910
 isofs_get_tree+0x1c/0x30 fs/isofs/inode.c:1539
 vfs_get_tree+0x57/0x1d0 fs/super.c:1947
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3772 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3848
 path_mount+0x4ad/0xb90 fs/namespace.c:4168
 do_mount fs/namespace.c:4181 [inline]
 __do_sys_mount fs/namespace.c:4397 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4374
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4374
 x64_sys_call+0xc3b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff888111455600 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 25035 Comm: syz.2.13296 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================
rock: corrupted directory entry. extent=134217760 out of volume (nzones=41)
netdevsim netdevsim2 eth3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim2 eth2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim2 eth1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim2 eth0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 03:54 upstream 66498c75b4f8 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru
* Struck through repros no longer work on HEAD.