syzbot


KCSAN: data-race in __se_sys_mremap / vms_complete_munmap_vmas

Status: moderation: reported on 2026/01/23 19:04
Subsystems: mm
Labels: race:benign
[Documentation on labels]
Reported-by: syzbot+55d5498eaf57f4739a2e@syzkaller.appspotmail.com
First crash: 4d10h, last: 4d10h

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

read-write to 0xffff888120891c88 of 4 bytes by task 5502 on cpu 0:
 vms_complete_munmap_vmas+0x54/0x440 mm/vma.c:1312
 __mmap_complete+0x4a/0x230 mm/vma.c:2581
 __mmap_region mm/vma.c:2761 [inline]
 mmap_region+0x1833/0x1aa0 mm/vma.c:2830
 do_mmap+0x9b2/0xbd0 mm/mmap.c:558
 vm_mmap_pgoff+0x183/0x2d0 mm/util.c:581
 ksys_mmap_pgoff+0xc1/0x310 mm/mmap.c:604
 x64_sys_call+0x16bb/0x3000 arch/x86/include/generated/asm/syscalls_64.h:10
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888120891c88 of 4 bytes by task 5513 on cpu 1:
 check_mremap_params mm/mremap.c:1820 [inline]
 do_mremap mm/mremap.c:1924 [inline]
 __do_sys_mremap mm/mremap.c:1997 [inline]
 __se_sys_mremap+0x43d/0xb50 mm/mremap.c:1965
 __x64_sys_mremap+0x67/0x80 mm/mremap.c:1965
 x64_sys_call+0x2944/0x3000 arch/x86/include/generated/asm/syscalls_64.h:26
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000033 -> 0x00000034

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5513 Comm: syz.2.540 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/23 19:03 upstream c072629f05d7 e2b1b6e6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __se_sys_mremap / vms_complete_munmap_vmas
* Struck through repros no longer work on HEAD.