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Date: Thu, 11 Apr 2024 12:55:13 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: syzbot <syzbot+ddf4b4c0005944105a9e@syzkaller.appspotmail.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
 syzkaller-bugs@googlegroups.com, Peter Xu <peterx@redhat.com>
Subject: Re: [syzbot] [mm?] WARNING in try_to_migrate_one (2)
Message-Id: <20240411125513.b779991117a4dea92ce77269@linux-foundation.org>
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On Wed, 10 Apr 2024 19:04:21 -0700 syzbot <syzbot+ddf4b4c0005944105a9e@syzkaller.appspotmail.com> wrote:

> syzbot has found a reproducer for the following issue on:

Thanks.

> HEAD commit:    480e035fc4c7 Merge tag 'drm-next-2024-03-13' of https://gi..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14db82bd180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1e5b814e91787669
> dashboard link: https://syzkaller.appspot.com/bug?extid=ddf4b4c0005944105a9e
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13111a4d180000

Seems to be userfaultfd related.

> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=156ae155180000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/5f73b6ef963d/disk-480e035f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/46c949396aad/vmlinux-480e035f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e3b4d0f5a5f8/bzImage-480e035f.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ddf4b4c0005944105a9e@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 5134 at arch/x86/include/asm/pgtable.h:404 pte_uffd_wp arch/x86/include/asm/pgtable.h:404 [inline]
> WARNING: CPU: 0 PID: 5134 at arch/x86/include/asm/pgtable.h:404 try_to_migrate_one+0x18e9/0x3ae0 mm/rmap.c:2256
> Modules linked in:
> CPU: 0 PID: 5134 Comm: syz-executor306 Not tainted 6.8.0-syzkaller-08073-g480e035fc4c7 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> RIP: 0010:pte_uffd_wp arch/x86/include/asm/pgtable.h:404 [inline]
> RIP: 0010:try_to_migrate_one+0x18e9/0x3ae0 mm/rmap.c:2256
> Code: ac ff 41 83 e7 42 bf 40 00 00 00 4c 89 fe e8 9e 74 ac ff 49 83 ff 40 0f 84 91 08 00 00 e8 af 6f ac ff eb 09 e8 a8 6f ac ff 90 <0f> 0b 90 49 83 cd 04 48 8b 3c 24 e8 b7 89 ff ff 89 c3 48 b8 00 00
> RSP: 0018:ffffc9000458f1e0 EFLAGS: 00010293
> RAX: ffffffff81e885a8 RBX: d000000000000000 RCX: ffff8880177a3c00
> RDX: 0000000000000000 RSI: 0000000000000400 RDI: 0000000000000000
> RBP: ffffc9000458f550 R08: ffffffff81e88560 R09: 1ffffd40003c10d8
> R10: dffffc0000000000 R11: fffff940003c10d9 R12: 0000000000000001
> R13: d7ffe7fff0fbc802 R14: 0000000000000002 R15: 000000007821bc67
> FS:  00007f2b2a0666c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f2b2a06b9f0 CR3: 0000000023ffe000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  rmap_walk_anon+0x36f/0x680 mm/rmap.c:2599
>  try_to_migrate+0x3de/0x4b0
>  migrate_folio_unmap mm/migrate.c:1244 [inline]
>  migrate_pages_batch+0x10b4/0x3570 mm/migrate.c:1675
>  migrate_pages_sync mm/migrate.c:1841 [inline]
>  migrate_pages+0x1eaf/0x3320 mm/migrate.c:1950
>  do_mbind mm/mempolicy.c:1344 [inline]
>  kernel_mbind mm/mempolicy.c:1486 [inline]
>  __do_sys_mbind mm/mempolicy.c:1560 [inline]
>  __se_sys_mbind+0x11f5/0x1a70 mm/mempolicy.c:1556
>  do_syscall_64+0xfb/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
> RIP: 0033:0x7f2b2a0af089
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 1a 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f2b2a066228 EFLAGS: 00000246 ORIG_RAX: 00000000000000ed
> RAX: ffffffffffffffda RBX: 00007f2b2a138408 RCX: 00007f2b2a0af089
> RDX: 0000000000000000 RSI: 0000000000003000 RDI: 0000000020ffd000
> RBP: 00007f2b2a138400 R08: 0000000000000000 R09: 0000000000000002
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2b2a1054f4
> R13: 0000000000000011 R14: 00007ffca01beb70 R15: 00007ffca01bec58
>  </TASK>
> 
> 
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.