[moderation] [mm?] KCSAN: data-race in __anon_vma_prepare / handle_mm_fault (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 27d128c1cff6 Merge tag 'trace-ring-buffer-v7.1-3' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12f1f1ba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2e40c0f41e01837e
dashboard link: https://syzkaller.appspot.com/bug?extid=fbdda2a8baef815acc22
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [Liam.H...@oracle.com ak...@linux-foundation.org da...@kernel.org ha...@kernel.org ja...@google.com linux-...@vger.kernel.org linu...@kvack.org l...@kernel.org ri...@surriel.com vba...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/297d9521c6ba/disk-27d128c1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a67992be46b3/vmlinux-27d128c1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/630edaa6f659/bzImage-27d128c1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fbdda2...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __anon_vma_prepare / handle_mm_fault

write to 0xffff888145dea040 of 8 bytes by task 8850 on cpu 0:
__anon_vma_prepare+0x172/0x2f0 mm/rmap.c:212
__vmf_anon_prepare mm/memory.c:3813 [inline]
vmf_anon_prepare mm/internal.h:503 [inline]
do_anonymous_page mm/memory.c:5372 [inline]
do_pte_missing mm/memory.c:4548 [inline]
handle_pte_fault mm/memory.c:6411 [inline]
__handle_mm_fault mm/memory.c:6549 [inline]
handle_mm_fault+0x24ae/0x2e70 mm/memory.c:6718
do_user_addr_fault+0x3fd/0x1050 arch/x86/mm/fault.c:1385
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
__put_user_4+0xd/0x20 arch/x86/lib/putuser.S:92
__sys_socketpair+0xa6/0x420 net/socket.c:1856
__do_sys_socketpair net/socket.c:1922 [inline]
__se_sys_socketpair net/socket.c:1919 [inline]
__x64_sys_socketpair+0x52/0x60 net/socket.c:1919
x64_sys_call+0x2de5/0x3020 arch/x86/include/generated/asm/syscalls_64.h:54
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888145dea040 of 8 bytes by task 8849 on cpu 1:
__vmf_anon_prepare mm/memory.c:3807 [inline]
vmf_anon_prepare mm/internal.h:503 [inline]
do_anonymous_page mm/memory.c:5372 [inline]
do_pte_missing mm/memory.c:4548 [inline]
handle_pte_fault mm/memory.c:6411 [inline]
__handle_mm_fault mm/memory.c:6549 [inline]
handle_mm_fault+0xff8/0x2e70 mm/memory.c:6718
do_user_addr_fault+0x62f/0x1050 arch/x86/mm/fault.c:1334
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

value changed: 0x0000000000000000 -> 0xffff88811a2c8780

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8849 Comm: syz.4.9406 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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