syzbot


KCSAN: data-race in __percpu_counter_init_many / copy_mm

Status: moderation: reported on 2025/05/19 18:56
Subsystems: ext4 mm
[Documentation on labels]
Reported-by: syzbot+5963acb161b25848dd87@syzkaller.appspotmail.com
First crash: 35d, last: 3d02h

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

write to 0xffff88810962f708 of 8 bytes by task 7305 on cpu 0:
 __list_add include/linux/list.h:153 [inline]
 list_add include/linux/list.h:169 [inline]
 __percpu_counter_init_many+0x292/0x310 lib/percpu_counter.c:220
 mm_init+0x6ac/0x850 kernel/fork.c:1076
 dup_mm kernel/fork.c:1473 [inline]
 copy_mm+0x101/0x370 kernel/fork.c:1529
 copy_process+0xcf1/0x1fe0 kernel/fork.c:2169
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 __do_sys_clone kernel/fork.c:2742 [inline]
 __se_sys_clone kernel/fork.c:2726 [inline]
 __x64_sys_clone+0xe6/0x120 kernel/fork.c:2726
 x64_sys_call+0x2c59/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810962f300 of 1408 bytes by task 8184 on cpu 1:
 dup_mm kernel/fork.c:1471 [inline]
 copy_mm+0xe2/0x370 kernel/fork.c:1529
 copy_process+0xcf1/0x1fe0 kernel/fork.c:2169
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 __do_sys_clone kernel/fork.c:2742 [inline]
 __se_sys_clone kernel/fork.c:2726 [inline]
 __x64_sys_clone+0xe6/0x120 kernel/fork.c:2726
 x64_sys_call+0x2c59/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8184 Comm: syz.5.1132 Not tainted 6.16.0-rc2-syzkaller-00269-g11313e2f7812 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/21 15:25 upstream 11313e2f7812 d6cdfb8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __percpu_counter_init_many / copy_mm
2025/06/04 21:54 upstream 1af80d00e1e0 e565f08d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __percpu_counter_init_many / copy_mm
2025/05/29 00:58 upstream 3d413f0cfd7e 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __percpu_counter_init_many / copy_mm
2025/05/19 18:55 upstream a5806cd506af b84f0537 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __percpu_counter_init_many / copy_mm
* Struck through repros no longer work on HEAD.