Re: [syzbot] WARNING in __split_huge_page_tail

[David Hildenbrand]

On 26.10.22 08:59, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    4da34b7d175d Merge tag 'thermal-6.1-rc2' of git://git.kern..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57
> dashboard link: https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8
> compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+273b547b15eb58ea35e8@xxxxxxxxxxxxxxxxxxxxxxxxx
>
>   tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363
>   exit_mmap+0x2b1/0x670 mm/mmap.c:3098
>   __mmput+0x114/0x3b0 kernel/fork.c:1185
>   exit_mm+0x217/0x2f0 kernel/exit.c:516
>   do_exit+0x5e7/0x2070 kernel/exit.c:807
>   do_group_exit+0x1fd/0x2b0 kernel/exit.c:950
>   __do_sys_exit_group kernel/exit.c:961 [inline]
>   __se_sys_exit_group kernel/exit.c:959 [inline]
>   __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959
>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>   do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465

Is this the

VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);

assertion?

--
Thanks,

David / dhildenb