syzbot


KCSAN: data-race in copy_mm / vms_complete_munmap_vmas

Status: moderation: reported on 2025/07/11 05:15
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+c47560027f2749bc292d@syzkaller.appspotmail.com
First crash: 6d10h, last: 6d10h

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

read-write to 0xffff88810005b230 of 4 bytes by task 9906 on cpu 0:
 vms_complete_munmap_vmas+0x55/0x440 mm/vma.c:1264
 __mmap_complete mm/vma.c:2519 [inline]
 __mmap_region mm/vma.c:2630 [inline]
 mmap_region+0x1167/0x1580 mm/vma.c:2692
 do_mmap+0x9b3/0xbe0 mm/mmap.c:561
 vm_mmap_pgoff+0x17a/0x2e0 mm/util.c:579
 ksys_mmap_pgoff+0xc2/0x310 mm/mmap.c:607
 x64_sys_call+0x1602/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:10
 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 0xffff88810005b180 of 1344 bytes by task 9908 on cpu 1:
 dup_mm kernel/fork.c:1471 [inline]
 copy_mm+0xe2/0x370 kernel/fork.c:1529
 copy_process+0xcf1/0x1f90 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: 9908 Comm: syz.3.1762 Not tainted 6.16.0-rc5-syzkaller-00121-gbc9ff192a6c9 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/11 05:15 upstream bc9ff192a6c9 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / vms_complete_munmap_vmas
* Struck through repros no longer work on HEAD.