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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bec6f00f120e Merge tag 'usb-6.15-rc6' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1649ecf4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6154604431d9aaf9
dashboard link: https://syzkaller.appspot.com/bug?extid=0a255278a17e4f418264
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linu...@kvack.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/41fdbe66c04f/disk-bec6f00f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1bf8be5bbf46/vmlinux-bec6f00f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a289eeedada0/bzImage-bec6f00f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0a2552...@syzkaller.appspotmail.com

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

write to 0xffff88810aaface8 of 8 bytes by task 31798 on cpu 0:
__list_add include/linux/list.h:153 [inline]
list_add include/linux/list.h:169 [inline]
try_to_unmap_one+0x134f/0x2140 mm/rmap.c:2170
rmap_walk_anon+0x27d/0x430 mm/rmap.c:2834
rmap_walk mm/rmap.c:2939 [inline]
try_to_unmap+0x13d/0x1e0 mm/rmap.c:2263
shrink_folio_list+0x121a/0x2670 mm/vmscan.c:1373
reclaim_folio_list+0x80/0x2b0 mm/vmscan.c:2217
reclaim_pages+0x215/0x270 mm/vmscan.c:2254
madvise_cold_or_pageout_pte_range+0xd61/0xdd0 mm/madvise.c:558
walk_pmd_range mm/pagewalk.c:130 [inline]
walk_pud_range mm/pagewalk.c:226 [inline]
walk_p4d_range mm/pagewalk.c:264 [inline]
walk_pgd_range+0x86b/0x11b0 mm/pagewalk.c:305
__walk_page_range+0xdd/0x340 mm/pagewalk.c:412
walk_page_range_mm+0x352/0x4a0 mm/pagewalk.c:505
walk_page_range+0x56/0x70 mm/pagewalk.c:584
madvise_pageout_page_range mm/madvise.c:617 [inline]
madvise_pageout mm/madvise.c:644 [inline]
madvise_vma_behavior mm/madvise.c:1269 [inline]
madvise_walk_vmas mm/madvise.c:1530 [inline]
madvise_do_behavior+0x1bea/0x24a0 mm/madvise.c:1695
do_madvise mm/madvise.c:1782 [inline]
__do_sys_madvise mm/madvise.c:1790 [inline]
__se_sys_madvise mm/madvise.c:1788 [inline]
__x64_sys_madvise+0xc9/0x100 mm/madvise.c:1788
x64_sys_call+0x2455/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:29
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810aafac00 of 1344 bytes by task 28578 on cpu 1:
dup_mm kernel/fork.c:1728 [inline]
copy_mm+0xfb/0x1310 kernel/fork.c:1786
copy_process+0xcf1/0x1f90 kernel/fork.c:2429
kernel_clone+0x16c/0x5b0 kernel/fork.c:2844
__do_sys_clone kernel/fork.c:2987 [inline]
__se_sys_clone kernel/fork.c:2971 [inline]
__x64_sys_clone+0xe6/0x120 kernel/fork.c:2971
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+0xd0/0x1a0 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: 28578 Comm: syz-executor Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
==================================================================


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[syzbot]

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