linux-kernel - Re: [PATCH 3/3] x86: mm: add x86_64 support for page table check

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Date:   Wed, 1 Dec 2021 09:44:44 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Pasha Tatashin <pasha.tatashin@...een.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, akpm@...ux-foundation.org,
        rientjes@...gle.com, pjt@...gle.com, weixugc@...gle.com,
        gthelen@...gle.com, mingo@...hat.com, corbet@....net,
        will@...nel.org, rppt@...nel.org, keescook@...omium.org,
        tglx@...utronix.de, peterz@...radead.org, masahiroy@...nel.org,
        samitolvanen@...gle.com, dave.hansen@...ux.intel.com,
        x86@...nel.org, frederic@...nel.org, hpa@...or.com,
        aneesh.kumar@...ux.ibm.com
Subject: Re: [PATCH 3/3] x86: mm: add x86_64 support for page table check

On 01. 12. 21, 9:00, Jiri Slaby wrote:
> On 23. 11. 21, 22:48, Pasha Tatashin wrote:
>> Add page table check hooks into routines that modify user page tables.
> 
> Hi,
> 
> I bisected to this as this causes crashes during modules load:

And it's not enough to unset CONFIG_PAGE_TABLE_CHECK_ENFORCED. I had to 
unset CONFIG_PAGE_TABLE_CHECK completely to get rid of this.

> #PF: supervisor write access in kernel mode
> #PF: error_code(0x0003) - permissions violation
> PGD 6d615067 P4D 6d615067 PUD 6d616063 PMD 800000006d2001e1
> Oops: 0003 [#1] PREEMPT SMP PTI
> CPU: 0 PID: 6189 Comm: modprobe Kdump: loaded Tainted: G          I E   
> 5.16.0-rc2-next-20211129-vanilla #3 
> 83846a405f0e3937f5c8dfbc7d449622b8f46369
> Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be 
> filled by O.E.M., BIOS SDBLI944.86P 05/08/2007
> RIP: 0010:jump_label_module_notify (kernel/jump_label.c:370 
> kernel/jump_label.c:670 kernel/jump_label.c:748)
> Code: 00 48 8b 43 08 a8 02 0f 85 e9 00 00 00 48 83 e0 fc 48 c7 02 00 00 
> 00 00 48 89 42 08 48 8b 43 08 83 e0 03 48 09 c2 48 83 ca 02 <48> 89 53 
> 08 4d 89 66 10 49 89 6e 08 48 8b 43 08 a8 02 0f 84 98 00
> All code
> ========
>     0:    00 48 8b                 add    %cl,-0x75(%rax)
>     3:    43 08 a8 02 0f 85 e9     rex.XB or %bpl,-0x167af0fe(%r8)
>     a:    00 00                    add    %al,(%rax)
>     c:    00 48 83                 add    %cl,-0x7d(%rax)
>     f:    e0 fc                    loopne 0xd
>    11:    48 c7 02 00 00 00 00     movq   $0x0,(%rdx)
>    18:    48 89 42 08              mov    %rax,0x8(%rdx)
>    1c:    48 8b 43 08              mov    0x8(%rbx),%rax
>    20:    83 e0 03                 and    $0x3,%eax
>    23:    48 09 c2                 or     %rax,%rdx
>    26:    48 83 ca 02              or     $0x2,%rdx
>    2a:*    48 89 53 08              mov    %rdx,0x8(%rbx)        <-- 
> trapping instruction
>    2e:    4d 89 66 10              mov    %r12,0x10(%r14)
>    32:    49 89 6e 08              mov    %rbp,0x8(%r14)
>    36:    48 8b 43 08              mov    0x8(%rbx),%rax
>    3a:    a8 02                    test   $0x2,%al
>    3c:    0f                       .byte 0xf
>    3d:    84                       .byte 0x84
>    3e:    98                       cwtl
>      ...
> 
> Code starting with the faulting instruction
> ===========================================
>     0:    48 89 53 08              mov    %rdx,0x8(%rbx)
>     4:    4d 89 66 10              mov    %r12,0x10(%r14)
>     8:    49 89 6e 08              mov    %rbp,0x8(%r14)
>     c:    48 8b 43 08              mov    0x8(%rbx),%rax
>    10:    a8 02                    test   $0x2,%al
>    12:    0f                       .byte 0xf
>    13:    84                       .byte 0x84
>    14:    98                       cwtl
>      ...
> RSP: 0018:ffffaf4dc051fbe8 EFLAGS: 00010282
> RAX: 0000000000000001 RBX: ffffffff931ee760 RCX: 0000000000000001
> RDX: ffff9d1aa7d43883 RSI: ffffffff91c50aa0 RDI: ffffffff931ee760
> RBP: ffffffffc0782000 R08: 0000000000000020 R09: 0000000000000000
> R10: ffff9d1aa7d43880 R11: 0000000000000000 R12: ffffffffc079a980
> R13: ffffffffc0784080 R14: ffff9d1aa7d43ca0 R15: ffffffffc0782008
> FS:  00007f87104b8740(0000) GS:ffff9d1b45c00000(0000) 
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffffff931ee768 CR3: 000000010fdce000 CR4: 00000000000006f0
> Call Trace:
>   <TASK>
> blocking_notifier_call_chain_robust (kernel/notifier.c:83 
> kernel/notifier.c:118 kernel/notifier.c:283 kernel/notifier.c:271)
> load_module (./include/linux/notifier.h:198 kernel/module.c:3923 
> kernel/module.c:4100)
> __do_sys_finit_module (kernel/module.c:4224)
> do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
> entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:113)
> 
>> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
>> ---
>>   arch/x86/Kconfig               |  1 +
>>   arch/x86/include/asm/pgtable.h | 29 +++++++++++++++++++++++++++--
>>   2 files changed, 28 insertions(+), 2 deletions(-)
>>
> 
> regards,


-- 
js
suse labs