Re: [syzbot] [mm?] WARNING in folio_walk_start

[David Hildenbrand <david@redhat.com>]

On 14.10.24 17:01, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    36c254515dc6 Merge tag 'powerpc-6.12-4' of git://git.kerne..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14edfb27980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=667b897270c8ae6
> dashboard link: https://syzkaller.appspot.com/bug?extid=7d917f67c05066cec295
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/62cbb10fcb60/disk-36c25451.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d63f77e475bd/vmlinux-36c25451.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/113b44f45a57/bzImage-36c25451.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+7d917f67c05066cec295@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 7022 at mm/pagewalk.c:815 folio_walk_start+0xef6/0x1160 mm/pagewalk.c:815
> Modules linked in:
> CPU: 1 UID: 0 PID: 7022 Comm: syz.3.435 Not tainted 6.12.0-rc2-syzkaller-00307-g36c254515dc6 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> RIP: 0010:folio_walk_start+0xef6/0x1160 mm/pagewalk.c:815
> Code: 90 0f 0b 90 49 81 ee 00 f0 ff 3f e9 1d f4 ff ff e8 8f b8 b1 ff 48 8b 7c 24 18 e8 85 9c 3a 09 e9 be f3 ff ff e8 7b b8 b1 ff 90 <0f> 0b 90 e9 22 f5 ff ff e8 6d b8 b1 ff 31 ff 89 ee e8 a4 ba b1 ff
> RSP: 0018:ffffc900096bfc80 EFLAGS: 00010287
> RAX: 0000000000004c5c RBX: ffff88807bc61c98 RCX: ffffc9000a2ba000
> RDX: 0000000000040000 RSI: ffffffff81db0095 RDI: 0000000000000007
> RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000080 R11: 0000000000000000 R12: fff00000001fffff
> R13: ffffc900096bfe28 R14: 0000000000000080 R15: ffff88802f484000
> FS:  00007f53545676c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000110c321de8 CR3: 0000000047274000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   add_folio_for_migration mm/migrate.c:2244 [inline]
>   do_pages_move mm/migrate.c:2346 [inline]
>   kernel_move_pages+0x619/0x15a0 mm/migrate.c:2553
>   __do_sys_move_pages mm/migrate.c:2567 [inline]
>   __se_sys_move_pages mm/migrate.c:2562 [inline]
>   __x64_sys_move_pages+0xe0/0x1c0 mm/migrate.c:2562
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f535377dff9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f5354567038 EFLAGS: 00000246 ORIG_RAX: 0000000000000117
> RAX: ffffffffffffffda RBX: 00007f5353936058 RCX: 00007f535377dff9
> RDX: 0000000020001100 RSI: 00000000000000d0 RDI: 0000000000000000
> RBP: 00007f53537f0296 R08: 0000000000000000 R09: 0000000000000002
> R10: 0000000020001140 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 00007f5353936058 R15: 00007ffec6628d18

I'm already investigating a related issue that popped up while talking 
to Jann: pmd_leaf() is only expressive when pmd_present(). It could 
explain the issue here.

I'll do some digging ...

-- 
Cheers,

David / dhildenb