[moderation] [mm?] KCSAN: data-race in copy_mm / mmap_region

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9dd1835ecda5 Merge tag 'dma-mapping-6.17-2025-09-09' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=108a5d62580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=3910b46eceeabb38e9be
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [Liam.H...@oracle.com ak...@linux-foundation.org ja...@google.com linux-...@vger.kernel.org linu...@kvack.org lorenzo...@oracle.com pfal...@suse.de vba...@suse.cz]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bed60878f1bb/disk-9dd1835e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7a737ddc0fed/vmlinux-9dd1835e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/39c2c269c318/bzImage-9dd1835e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3910b4...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in copy_mm / mmap_region

read-write to 0xffff8881042c3470 of 4 bytes by task 20460 on cpu 0:
__mmap_new_vma mm/vma.c:2498 [inline]
__mmap_region mm/vma.c:2669 [inline]
mmap_region+0x112b/0x1630 mm/vma.c:2739
do_mmap+0x9b3/0xbe0 mm/mmap.c:558
vm_mmap_pgoff+0x17a/0x2e0 mm/util.c:580
ksys_mmap_pgoff+0x268/0x310 mm/mmap.c:604
x64_sys_call+0x14a3/0x2ff0 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 0xffff8881042c33c0 of 1408 bytes by task 20462 on cpu 1:
dup_mm kernel/fork.c:1479 [inline]
copy_mm+0xe2/0x370 kernel/fork.c:1537
copy_process+0xd08/0x2000 kernel/fork.c:2175
kernel_clone+0x16c/0x5c0 kernel/fork.c:2605
__do_sys_clone kernel/fork.c:2748 [inline]
__se_sys_clone kernel/fork.c:2732 [inline]
__x64_sys_clone+0xe6/0x120 kernel/fork.c:2732
x64_sys_call+0x119c/0x2ff0 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: 20462 Comm: syz.3.5645 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================
lo speed is unknown, defaulting to 1000
lo speed is unknown, defaulting to 1000
lo speed is unknown, defaulting to 1000


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.