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 09:00:00 +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 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:
#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