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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8c2e52ebbe88 eventpoll: don't decrement ep refcount while ..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11fb1bd4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a2f5ccd29a82f8aa
dashboard link: https://syzkaller.appspot.com/bug?extid=5c8b83125b441768bb5f
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
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/ee73aee8bfc2/disk-8c2e52eb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a9a09d48eb93/vmlinux-8c2e52eb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cf45f219483f/bzImage-8c2e52eb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5c8b83...@syzkaller.appspotmail.com

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

read-write to 0xffff88810bcce930 of 4 bytes by task 9214 on cpu 0:
vma_complete+0x13f/0x580 mm/vma.c:352
__split_vma+0x5d9/0x650 mm/vma.c:565
split_vma mm/vma.c:595 [inline]
vma_modify+0x3f2/0xc80 mm/vma.c:1626
vma_modify_flags+0x101/0x130 mm/vma.c:1644
mprotect_fixup+0x2cc/0x570 mm/mprotect.c:658
do_mprotect_pkey+0x6d6/0x980 mm/mprotect.c:832
__do_sys_mprotect mm/mprotect.c:853 [inline]
__se_sys_mprotect mm/mprotect.c:850 [inline]
__x64_sys_mprotect+0x48/0x60 mm/mprotect.c:850
x64_sys_call+0x2794/0x2fb0 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 0xffff88810bcce880 of 1344 bytes by task 9216 on cpu 1:
dup_mm kernel/fork.c:1471 [inline]
copy_mm+0xe2/0x370 kernel/fork.c:1529
copy_process+0xcf1/0x1f90 kernel/fork.c:2169
kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
__do_sys_clone kernel/fork.c:2742 [inline]
__se_sys_clone kernel/fork.c:2726 [inline]
__x64_sys_clone+0xe6/0x120 kernel/fork.c:2726
x64_sys_call+0x2c59/0x2fb0 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: 9216 Comm: syz.3.2155 Not tainted 6.16.0-rc5-syzkaller-00053-g8c2e52ebbe88 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


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[syzbot]

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