[moderation] [mm?] KCSAN: data-race in copy_mm / vma_complete (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9b332cece987 Merge tag 'nfsd-6.18-1' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12e9152f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=bafeb347352dd60e
dashboard link: https://syzkaller.appspot.com/bug?extid=93b9f9203fe921d1b0b1
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/2fd7b9202667/disk-9b332cec.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bb13089219f4/vmlinux-9b332cec.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0bb4f4518530/bzImage-9b332cec.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+93b9f9...@syzkaller.appspotmail.com

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

read-write to 0xffff88810005d6f0 of 4 bytes by task 9098 on cpu 1:
vma_complete+0x13f/0x580 mm/vma.c:355
__split_vma+0x591/0x650 mm/vma.c:568
split_vma mm/vma.c:598 [inline]
vma_modify+0x21e/0xc80 mm/vma.c:1623
vma_modify_flags+0x101/0x130 mm/vma.c:1649
mprotect_fixup+0x2cc/0x570 mm/mprotect.c:816
do_mprotect_pkey+0x6d6/0x980 mm/mprotect.c:990
__do_sys_mprotect mm/mprotect.c:1011 [inline]
__se_sys_mprotect mm/mprotect.c:1008 [inline]
__x64_sys_mprotect+0x48/0x60 mm/mprotect.c:1008
x64_sys_call+0x2752/0x3000 arch/x86/include/generated/asm/syscalls_64.h:11
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 0xffff88810005d640 of 1408 bytes by task 9102 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: 9102 Comm: syz.0.1924 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================


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