syzbot


KCSAN: data-race in copy_mm / lru_gen_del_mm

Status: moderation: reported on 2026/01/18 18:46
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+2e51198bb1b40e8ab1cf@syzkaller.appspotmail.com
First crash: 45d, last: 6d11h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
8ea1dd16-e991-44d2-898d-876fe77775fb assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in copy_mm / lru_gen_del_mm 2026/01/18 18:45 2026/01/18 18:45 2026/01/18 18:58 a9d6a79219801d2130df3b1a792c57f0e5428e9f

Sample crash report:
==================================================================
BUG: KCSAN: data-race in copy_mm / lru_gen_del_mm

write to 0xffff88810eb293b8 of 8 bytes by task 9731 on cpu 1:
 __list_del include/linux/list.h:203 [inline]
 __list_del_entry include/linux/list.h:226 [inline]
 list_del_init include/linux/list.h:295 [inline]
 lru_gen_del_mm+0x28a/0x3e0 mm/vmscan.c:2959
 __mmput+0x17a/0x1c0 kernel/fork.c:1184
 mmput+0x40/0x50 kernel/fork.c:1197
 exit_mm+0xe3/0x180 kernel/exit.c:581
 do_exit+0x3fa/0x15a0 kernel/exit.c:959
 do_group_exit+0x138/0x140 kernel/exit.c:1112
 __do_sys_exit_group kernel/exit.c:1123 [inline]
 __se_sys_exit_group kernel/exit.c:1121 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1121
 x64_sys_call+0x3008/0x3020 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810eb28d80 of 1664 bytes by task 9732 on cpu 0:
 dup_mm kernel/fork.c:1524 [inline]
 copy_mm+0xe1/0x370 kernel/fork.c:1582
 copy_process+0xe22/0x20d0 kernel/fork.c:2223
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2654
 __do_sys_clone kernel/fork.c:2795 [inline]
 __se_sys_clone kernel/fork.c:2779 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2779
 x64_sys_call+0x1222/0x3020 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9732 Comm: dhcpcd-run-hook Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/27 06:39 upstream 3f4a08e64442 a2f13f71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / lru_gen_del_mm
2026/01/30 13:08 upstream 4d310797262f ae7dc18c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / lru_gen_del_mm
2026/01/18 18:45 upstream e84d960149e7 20d37d28 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / lru_gen_del_mm
* Struck through repros no longer work on HEAD.