syzbot

ID	Workflow	Result	Correct	Bug	Created	Started	Finished	Revision	Error
76f77e81-13ac-425e-9ce3-e0e06468ea58	assessment-kcsan		💥	KCSAN: data-race in __find_get_block / has_bh_in_lru	2026/01/12 18:21	2026/01/12 18:21	2026/01/12 18:24	dc57dbf3ee402bd8ad9c3037d56ee9d9940a9bc6	failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "128" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/d80fe6a1a3bbd55c0c3eef45a0cf8dfd44a3ac0c" "bzImage" "compile_commands.json"]: exit status 2

==================================================================
BUG: KCSAN: data-race in __find_get_block / has_bh_in_lru

read-write to 0xffff888237d2a448 of 8 bytes by task 3114 on cpu 1:
 bh_lru_install fs/buffer.c:1340 [inline]
 __find_get_block+0x409/0x890 fs/buffer.c:1403
 bdev_getblk+0x35/0x7a0 fs/buffer.c:1423
 __getblk include/linux/buffer_head.h:358 [inline]
 sb_getblk include/linux/buffer_head.h:364 [inline]
 ext4_getblk+0x1c1/0x510 fs/ext4/inode.c:841
 ext4_bread+0x2c/0x110 fs/ext4/inode.c:887
 __ext4_read_dirblock+0x77/0x5a0 fs/ext4/namei.c:144
 htree_dirblock_to_tree+0x102/0x630 fs/ext4/namei.c:1082
 ext4_htree_fill_tree+0x429/0x9b0 fs/ext4/namei.c:1219
 ext4_dx_readdir fs/ext4/dir.c:597 [inline]
 ext4_readdir+0x15b0/0x1ac0 fs/ext4/dir.c:142
 iterate_dir+0x128/0x300 fs/readdir.c:106
 __do_sys_getdents64 fs/readdir.c:405 [inline]
 __se_sys_getdents64+0x88/0x1a0 fs/readdir.c:390
 __x64_sys_getdents64+0x43/0x50 fs/readdir.c:390
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888237d2a448 of 8 bytes by task 3102 on cpu 0:
 has_bh_in_lru+0x35/0x1e0 fs/buffer.c:1510
 cpu_needs_drain mm/swap.c:802 [inline]
 __lru_add_drain_all+0x254/0x420 mm/swap.c:889
 lru_add_drain_all+0x10/0x20 mm/swap.c:905
 invalidate_bdev+0x54/0x70 block/bdev.c:86
 ext4_put_super+0x51b/0x7e0 fs/ext4/super.c:1361
 generic_shutdown_super+0xdb/0x210 fs/super.c:696
 kill_block_super+0x2a/0x60 fs/super.c:1667
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7330
 deactivate_locked_super+0x7a/0x1c0 fs/super.c:484
 deactivate_super+0x9b/0xb0 fs/super.c:517
 cleanup_mnt+0x272/0x2e0 fs/namespace.c:1256
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1263
 task_work_run+0x135/0x1a0 kernel/task_work.c:180
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xd6/0xe0 kernel/entry/common.c:171
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296
 do_syscall_64+0x50/0x110 arch/x86/entry/common.c:88
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000000000 -> 0xffff8881053bbf70

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3102 Comm: syz-executor.0 Not tainted 6.7.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
==================================================================