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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5bde837031a3 Merge tag 'pci-v6.19-fixes-4' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14b2805a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6c9e86480ac654d3
dashboard link: https://syzkaller.appspot.com/bug?extid=201577f534f2b6980242
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 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/caeacd1178ce/disk-5bde8370.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/25377372b14c/vmlinux-5bde8370.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9668447d58db/bzImage-5bde8370.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+201577...@syzkaller.appspotmail.com

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

read-write to 0xffff88810005b644 of 4 bytes by task 17845 on cpu 1:
mt_set_height lib/maple_tree.c:218 [inline]
mas_put_in_tree lib/maple_tree.c:1556 [inline]
mas_topiary_replace lib/maple_tree.c:2341 [inline]
mas_wmb_replace+0x1a7/0xfa0 lib/maple_tree.c:2433
mas_split lib/maple_tree.c:3052 [inline]
mas_commit_b_node lib/maple_tree.c:3072 [inline]
mas_wr_bnode lib/maple_tree.c:3739 [inline]
mas_wr_store_entry+0x1610/0x2990 lib/maple_tree.c:3771
mas_store_prealloc+0x72e/0xa60 lib/maple_tree.c:5169
vma_iter_store_overwrite mm/vma.h:544 [inline]
vma_iter_store_new+0x1c5/0x200 mm/vma.h:551
vma_complete+0x125/0x580 mm/vma.c:353
__split_vma+0x5e3/0x660 mm/vma.c:566
split_vma mm/vma.c:596 [inline]
vma_modify+0xbcb/0xd30 mm/vma.c:1674
vma_modify_flags+0x182/0x210 mm/vma.c:1694
mprotect_fixup+0x30e/0x5e0 mm/mprotect.c:756
do_mprotect_pkey+0x67b/0x920 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+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810005b600 of 1664 bytes by task 17847 on cpu 0:
dup_mm kernel/fork.c:1523 [inline]
copy_mm+0xe1/0x370 kernel/fork.c:1581
copy_process+0xcbd/0x1f10 kernel/fork.c:2221
kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
__do_sys_clone kernel/fork.c:2792 [inline]
__se_sys_clone kernel/fork.c:2776 [inline]
__x64_sys_clone+0x143/0x180 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+0xc0/0x2a0 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: 17847 Comm: syz.1.3439 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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