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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2eba5e05d9bc Merge tag 'loongarch-fixes-6.18-2' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15cada12580000
kernel config: https://syzkaller.appspot.com/x/.config?x=655255e3ef31c19b
dashboard link: https://syzkaller.appspot.com/bug?extid=2059e2b89f863d20238b
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/c8f29f4a69c2/disk-2eba5e05.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d84d88612df0/vmlinux-2eba5e05.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c13e871004e/bzImage-2eba5e05.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2059e2...@syzkaller.appspotmail.com

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

read-write to 0xffff8881022ed738 of 4 bytes by task 17393 on cpu 1:
do_raw_write_seqcount_begin include/linux/seqlock.h:431 [inline]
mm_lock_seqcount_begin include/linux/mmap_lock.h:88 [inline]
mmap_write_lock_killable include/linux/mmap_lock.h:332 [inline]
vm_mmap_pgoff+0x126/0x2e0 mm/util.c:579
ksys_mmap_pgoff+0xc2/0x310 mm/mmap.c:604
x64_sys_call+0x14a3/0x3000 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 0xffff8881022ed640 of 1408 bytes by task 17396 on cpu 0:
dup_mm kernel/fork.c:1483 [inline]
copy_mm+0xe2/0x370 kernel/fork.c:1541
copy_process+0xd08/0x2000 kernel/fork.c:2181
kernel_clone+0x16c/0x5c0 kernel/fork.c:2609
__do_sys_clone3 kernel/fork.c:2911 [inline]
__se_sys_clone3+0x1c2/0x200 kernel/fork.c:2890
__x64_sys_clone3+0x31/0x40 kernel/fork.c:2890
x64_sys_call+0x1fc9/0x3000 arch/x86/include/generated/asm/syscalls_64.h:436
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: 0 UID: 0 PID: 17396 Comm: syz.7.4613 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================


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