[moderation] [mm?] KCSAN: data-race in copy_mm / vma_complete (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ccd1cdca5cd4 Merge tag 'nfsd-6.19-1' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=127dab92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=066a77caae64cfbe489b
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/12fc5a9ed91b/disk-ccd1cdca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b6208e3d3a67/vmlinux-ccd1cdca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/785c07926b9a/bzImage-ccd1cdca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+066a77...@syzkaller.appspotmail.com

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

read-write to 0xffff88810b36d948 of 4 bytes by task 8104 on cpu 1:
vma_complete+0x13f/0x580 mm/vma.c:349
__split_vma+0x59b/0x660 mm/vma.c:561
split_vma mm/vma.c:591 [inline]
vma_modify+0xb53/0xd50 mm/vma.c:1626
vma_modify_flags+0x10c/0x190 mm/vma.c:1654
mprotect_fixup+0x30f/0x5e0 mm/mprotect.c:756
do_mprotect_pkey+0x6d6/0x980 mm/mprotect.c:930
__do_sys_mprotect mm/mprotect.c:951 [inline]
__se_sys_mprotect mm/mprotect.c:948 [inline]
__x64_sys_mprotect+0x48/0x60 mm/mprotect.c:948
x64_sys_call+0x2c3b/0x3000 arch/x86/include/generated/asm/syscalls_64.h:11
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810b36d7c0 of 1664 bytes by task 8105 on cpu 0:
dup_mm kernel/fork.c:1523 [inline]
copy_mm+0xe2/0x370 kernel/fork.c:1581
copy_process+0xcbc/0x1ef0 kernel/fork.c:2221
kernel_clone+0x16c/0x5c0 kernel/fork.c:2651
__do_sys_clone kernel/fork.c:2792 [inline]
__se_sys_clone kernel/fork.c:2776 [inline]
__x64_sys_clone+0xe6/0x120 kernel/fork.c:2776
x64_sys_call+0x12d0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:57
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 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: 8105 Comm: syz.1.924 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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