Re: [syzbot] [mm?] kernel BUG in page_table_check_set

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

Andrew Morton <akpm@linux-foundation.org> writes:

> On Thu, 21 Aug 2025 21:16:32 -0700 syzbot <syzbot+49a796ed2c9709652f1e@syzkaller.appspotmail.com> wrote:
>
>> Hello,
>> 
>> syzbot found the following issue on:
>> 
>> HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
>> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
>> console output: https://syzkaller.appspot.com/x/log.txt?x=15f926f0580000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5ac3d8b8abfcb
>> dashboard link: https://syzkaller.appspot.com/bug?extid=49a796ed2c9709652f1e
>> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
>> userspace arch: arm64
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15faa7a2580000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=144143bc580000
>> 
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/18a2e4bd0c4a/disk-8f5ae30d.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/3b5395881b25/vmlinux-8f5ae30d.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/e875f4e3b7ff/Image-8f5ae30d.gz.xz
>> 
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+49a796ed2c9709652f1e@syzkaller.appspotmail.com
>> 
>> ------------[ cut here ]------------
>> kernel BUG at mm/page_table_check.c:118!
>
> Thanks.
>
> Presumably due to the series "Support page table check on PowerPC". 

The syzbot triggered this on:
 HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
 git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci

This tree does not have "Support page table check on PowerPC", correct?

Also, I guess Dev's change fixes this reported problem which could happen in
this path: commit_anon_folio_batch() -> change_pte_range() ... 

[1]: https://lore.kernel.org/all/20250812060124.C9344C4CEF0@smtp.kernel.org/
[2]: https://lore.kernel.org/all/68a80cc6.050a0220.3809a8.0002.GAE@google.com/

-ritesh


> Andrew, could you please take a look?
>
> The series has been in mm.git for a week so I guess the impact of this
> is small.  I won't drop it at this time, but prompt attention would be
> appreciated.
>
>> Internal error: Oops - BUG: 00000000f2000800 [#1]  SMP
>> Modules linked in:
>> CPU: 1 UID: 0 PID: 6740 Comm: syz.0.17 Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0 PREEMPT 
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
>> pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
>> pc : page_table_check_set+0x584/0x590 mm/page_table_check.c:118
>> lr : page_table_check_set+0x584/0x590 mm/page_table_check.c:118
>> sp : ffff80009c9674c0
>> x29: ffff80009c9674d0 x28: ffff80008fae0000 x27: 0000000000000002
>> x26: ffff0000c079ca80 x25: 0000000000000001 x24: 0000000000000001
>> x23: ffff0000c079ca80 x22: 000000000012b950 x21: 0000000000000001
>> x20: 0000000000000003 x19: 1ffff00012eb65b0 x18: 0000000000000000
>> x17: 0000000000000000 x16: ffff800080528a28 x15: 0000000000000001
>> x14: 1fffe000180f3950 x13: 0000000000000000 x12: 0000000000000000
>> x11: ffff6000180f3951 x10: 0000000000ff0100 x9 : 0000000000000000
>> x8 : ffff0000cdb05b80 x7 : ffff800080d16554 x6 : 0000000000000000
>> x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff800080d15b5c
>> x2 : 0000000000000001 x1 : 0000000000000002 x0 : 0000000000000001
>> Call trace:
>>  page_table_check_set+0x584/0x590 mm/page_table_check.c:118 (P)
>>  __page_table_check_ptes_set+0x2a8/0x2e0 mm/page_table_check.c:209
>>  page_table_check_ptes_set include/linux/page_table_check.h:76 [inline]
>>  __set_ptes_anysz arch/arm64/include/asm/pgtable.h:709 [inline]
>>  __set_ptes+0x4a0/0x504 arch/arm64/include/asm/pgtable.h:741
>>  contpte_set_ptes+0x120/0x188 arch/arm64/mm/contpte.c:464
>>  set_ptes arch/arm64/include/asm/pgtable.h:1794 [inline]
>>  modify_prot_commit_ptes+0x4e4/0x694 arch/arm64/mm/mmu.c:1556
>>  prot_commit_flush_ptes mm/mprotect.c:197 [inline]
>>  commit_anon_folio_batch mm/mprotect.c:246 [inline]
>>  set_write_prot_commit_flush_ptes mm/mprotect.c:273 [inline]
>>  change_pte_range mm/mprotect.c:354 [inline]
>>  change_pmd_range mm/mprotect.c:570 [inline]
>>  change_pud_range mm/mprotect.c:633 [inline]
>>  change_p4d_range mm/mprotect.c:659 [inline]
>>  change_protection_range mm/mprotect.c:687 [inline]
>>  change_protection+0x1e84/0x3ff0 mm/mprotect.c:721
>>  mprotect_fixup+0x504/0x744 mm/mprotect.c:837
>>  do_mprotect_pkey+0x864/0xb30 mm/mprotect.c:993
>>  __do_sys_mprotect mm/mprotect.c:1014 [inline]
>>  __se_sys_mprotect mm/mprotect.c:1011 [inline]
>>  __arm64_sys_mprotect+0x80/0x98 mm/mprotect.c:1011
>>  __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
>>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
>>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
>>  el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879
>>  el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
>>  el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
>> Code: d4210000 97e865fd d4210000 97e865fb (d4210000) 
>> ---[ end trace 0000000000000000 ]---
>> 
>> 
>> ---
>> This report is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@googlegroups.com.
>> 
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>> 
>> If the report is already addressed, let syzbot know by replying with:
>> #syz fix: exact-commit-title
>> 
>> 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.
>> 
>> If you want to overwrite report's subsystems, reply with:
>> #syz set subsystems: new-subsystem
>> (See the list of subsystem names on the web dashboard)
>> 
>> If the report is a duplicate of another one, reply with:
>> #syz dup: exact-subject-of-another-report
>> 
>> If you want to undo deduplication, reply with:
>> #syz undup