Re: [syzbot] [mm?] [io-uring?] WARNING in hpage_collapse_scan_pmd (2)

[David Hildenbrand <david@redhat.com>]

On 03.05.24 15:41, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    e67572cd2204 Linux 6.9-rc6
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1067d2f8980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3310e643b6ef5d69
> dashboard link: https://syzkaller.appspot.com/bug?extid=5ea2845f44caa77f5543
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10874a40980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d3c4905a7f32/disk-e67572cd.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/9e4d1fc8f9c1/vmlinux-e67572cd.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4616b77edaee/bzImage-e67572cd.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5ea2845f44caa77f5543@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 5288 at arch/x86/include/asm/pgtable.h:403 pte_uffd_wp arch/x86/include/asm/pgtable.h:403 [inline]
> WARNING: CPU: 1 PID: 5288 at arch/x86/include/asm/pgtable.h:403 hpage_collapse_scan_pmd+0xd32/0x14c0 mm/khugepaged.c:1316

That's the

WARN_ON_ONCE(wp && pte_write(pte));

check during pte_uffd_wp() in hpage_collapse_scan_pmd().

Maybe fixed by

commit fffa0c5024e8c90dced69b7fcde1d738384a1069
Author: Peter Xu <peterx@redhat.com>
Date:   Mon Apr 22 09:33:11 2024 -0400

     mm/userfaultfd: reset ptes when close() for wr-protected ones


That resides in mm-hotfixes-unstable

(in which case we might want to tag it as stable)


> Modules linked in:
> CPU: 1 PID: 5288 Comm: syz-executor.4 Not tainted 6.9.0-rc6-syzkaller #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:403 [inline]
> RIP: 0010:hpage_collapse_scan_pmd+0xd32/0x14c0 mm/khugepaged.c:1316
> Code: 90 90 e9 4b f6 ff ff 4c 8b 64 24 48 e8 f7 ee 9e ff 31 ff 4c 89 ee e8 fd e9 9e ff 4d 85 ed 0f 84 b5 01 00 00 e8 df ee 9e ff 90 <0f> 0b 90 41 be 09 00 00 00 0f b6 6c 24 47 48 8b 5c 24 10 e9 fb fa
> RSP: 0018:ffffc90003abf9b0 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff88807a402000 RCX: ffffffff81eed643
> RDX: ffff888021ddbc00 RSI: ffffffff81eed651 RDI: 0000000000000007
> RBP: 000000006897fc67 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000002 R11: 0000000000000002 R12: 0000000020800000
> R13: 0000000000000002 R14: 0000000000000400 R15: ffff88801e4dcc00
> FS:  00007fd661dde6c0(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f7e57ed9ba1 CR3: 0000000025328000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   madvise_collapse+0x738/0xb10 mm/khugepaged.c:2761
>   madvise_vma_behavior+0x202/0x1b20 mm/madvise.c:1074
>   madvise_walk_vmas+0x1cf/0x2c0 mm/madvise.c:1248
>   do_madvise+0x309/0x640 mm/madvise.c:1428
>   __do_sys_madvise mm/madvise.c:1441 [inline]
>   __se_sys_madvise mm/madvise.c:1439 [inline]
>   __x64_sys_madvise+0xa9/0x110 mm/madvise.c:1439
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd66227dea9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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:00007fd661dde0c8 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
> RAX: ffffffffffffffda RBX: 00007fd6623ac050 RCX: 00007fd66227dea9
> RDX: 0000000000000019 RSI: 00000000dfc3efff RDI: 00000000203c1000
> RBP: 00007fd6622ca4a4 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 000000000000006e R14: 00007fd6623ac050 R15: 00007ffd98c8dfa8
>   </TASK>
> 
> 
> ---
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> 
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> If the report is already addressed, let syzbot know by replying with:
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> 
> If you want syzbot to run the reproducer, reply with:
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> If you attach or paste a git patch, syzbot will apply it before testing.

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-hotfixes-unstable

-- 
Cheers,

David / dhildenb