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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 502d801f0ab0 Merge tag 'erofs-for-7.2-rc1' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11fe14d0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4d0f6c16a80c07db
dashboard link: https://syzkaller.appspot.com/bug?extid=b32400c5849c582dabad
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
CC: [ak...@linux-foundation.org ja...@google.com li...@infradead.org linux-...@vger.kernel.org linu...@kvack.org l...@kernel.org pfal...@suse.de vba...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7a2ab34be1f7/disk-502d801f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/344e858ce175/vmlinux-502d801f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/269d734808e7/bzImage-502d801f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b32400...@syzkaller.appspotmail.com

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

read-write to 0xffff888128390208 of 4 bytes by task 28450 on cpu 0:
do_raw_write_seqcount_begin include/linux/seqlock.h:432 [inline]
mm_lock_seqcount_begin include/linux/mmap_lock.h:125 [inline]
mmap_write_lock_killable include/linux/mmap_lock.h:556 [inline]
vm_mmap_pgoff+0x12f/0x2d0 mm/util.c:579
ksys_mmap_pgoff+0xc1/0x310 mm/mmap.c:606
x64_sys_call+0x14df/0x3020 arch/x86/include/generated/asm/syscalls_64.h:10
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888128390000 of 1728 bytes by task 28451 on cpu 1:
dup_mm kernel/fork.c:1532 [inline]
copy_mm+0xd6/0x340 kernel/fork.c:1590
copy_process+0x10cd/0x2350 kernel/fork.c:2288
kernel_clone+0x1c0/0x5f0 kernel/fork.c:2746
__do_sys_clone kernel/fork.c:2887 [inline]
__se_sys_clone kernel/fork.c:2871 [inline]
__x64_sys_clone+0x143/0x180 kernel/fork.c:2871
x64_sys_call+0x1222/0x3020 arch/x86/include/generated/asm/syscalls_64.h:57
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 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: 28451 Comm: syz.1.7631 Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================


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