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Date:   Thu, 9 Jun 2022 11:11:42 +0200
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Subject: Re: [PATCH V3 0/7] x86/entry: Convert error_entry() to C code
Content-Language: en-US
To:     Lai Jiangshan <jiangshanlai@gmail.com>,
        linux-kernel@vger.kernel.org
Cc:     Borislav Petkov <bp@alien8.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        Lai Jiangshan <jiangshan.ljs@antgroup.com>
References: <20220606144509.617611-1-jiangshanlai@gmail.com>
From:   Vegard Nossum <vegard.nossum@oracle.com>
In-Reply-To: <20220606144509.617611-1-jiangshanlai@gmail.com>
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On 6/6/22 16:45, Lai Jiangshan wrote:
> From: Lai Jiangshan <jiangshan.ljs@antgroup.com>
> 
> Add some C equivalent functions of the ASM macros and implement the whole
> error_entry() as C code.

Hi,

I did some testing of your patches (on top of mainline commit
34f4335c16a5) and I see these two KASAN reports very occasionally during
boot:

1)

Mountpoint-cache hash table entries: 2048 (order: 2, 16384 bytes, linear)
==================================================================
BUG: KASAN: wild-memory-access in rcu_nmi_enter+0x6e/0xf0
Read of size 4 at addr ff11000034e38b10 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc1-14003-ga9afe081e27d
#1787
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x57/0x7d
 ? rcu_nmi_enter+0x6e/0xf0
 print_report.cold+0x188/0x667
 ? rcu_nmi_enter+0x6e/0xf0
 kasan_report+0x8a/0x1b0
 ? rcu_nmi_enter+0x6e/0xf0
 kasan_check_range+0x14d/0x1d0
 rcu_nmi_enter+0x6e/0xf0
 irqentry_enter+0x33/0x50
 common_interrupt+0x15/0xc0
 asm_common_interrupt+0x2a/0x40
RIP: 0010:identify_cpu+0x3db/0x19f0
Code: b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 d3 14
00 00 41 c7 84 24 80 00 00 00 00 00 00 00 31 c0 89 c1 0f a2 <41> 89 54
24 7c 4c 89 e2 41 89 44 24 1c 48 c1 ea 03 48 b8 00 00 00
RSP: 0000:ffffffff94807da0 EFLAGS: 00000246
RAX: 000000000000001b RBX: 00000000756e6547 RCX: 000000006c65746e
RDX: 0000000049656e69 RSI: 0000000000000000 RDI: ffffffff9509e6e0
RBP: ffffffff9509e675 R08: ffffffff9509e67c R09: 0000000000000000
R10: ffffffff9509e668 R11: fffffbfff2a13cce R12: ffffffff9509e660
R13: ffffffff9509e6e8 R14: ffffffff9509e678 R15: ffffffff9509e674
 identify_boot_cpu+0xd/0xb5
 check_bugs+0x82/0x15b5
 ? l1tf_cmdline+0x10c/0x10c
 ? do_raw_spin_unlock+0x4f/0x250
 ? _raw_spin_unlock+0x24/0x40
 ? poking_init+0x350/0x37f
 ? parse_direct_gbpages_off+0xd/0xd
 ? rcu_read_lock_bh_held+0xc0/0xc0
 start_kernel+0x38c/0x3bb
 secondary_startup_64_no_verify+0xe0/0xeb
 </TASK>
==================================================================
Disabling lock debugging due to kernel taint
x86/cpu: User Mode Instruction Prevention (UMIP) activated
numa_add_cpu cpu 0 node 0: mask now 0

2)

x86/cpu: User Mode Instruction Prevention (UMIP) activated
numa_add_cpu cpu 0 node 0: mask now 0
Last level iTLB entries: 4KB 0, 2MB 0, 4MB 0
Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0, 1GB 0
Spectre V1 : Vulnerable: __user pointer sanitization and usercopy
barriers only; no swapgs barriers
Spectre V2 : Mitigation: Enhanced IBRS
Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling RSB on context
switch
Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction
Barrier
Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled
TAA: Mitigation: TSX disabled
==================================================================
BUG: KASAN: out-of-bounds in rcu_nmi_enter+0x6e/0xf0
Read of size 4 at addr ff11000034e38b10 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc1-14003-ga9afe081e27d
#1787
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x57/0x7d
 print_report.cold+0x9c/0x667
 ? rcu_nmi_enter+0x6e/0xf0
 kasan_report+0x8a/0x1b0
 ? rcu_nmi_enter+0x6e/0xf0
 kasan_check_range+0x14d/0x1d0
 rcu_nmi_enter+0x6e/0xf0
 irqentry_enter+0x33/0x50
 common_interrupt+0x15/0xc0
 asm_common_interrupt+0x2a/0x40
RIP: 0010:text_poke_early+0x97/0x9e
Code: 8e 00 f8 fd 48 85 db 74 01 fb eb 05 0f 1f 00 eb 16 8c d0 50 54 48
83 04 24 08 9c 8c c8 50 68 13 ec 12 b1 48 cf eb 03 0f 01 e8 <5b> 5d 41
5c 41 5d c3 41 57 b8 ff ff 37 00 41 56 48 c1 e0 2a 41 55
RSP: 0000:ffffffffb0007c10 EFLAGS: 00000292
RAX: 0000000000000010 RBX: 0000000000000200 RCX: 1ffffffff61137c9
RDX: 0000000000000000 RSI: ffffffffaf69f720 RDI: ffffffffaf7f9ce0
RBP: ffffffffacc6902c R08: 0000000000000001 R09: 0000000000000001
R10: ffffffffacc69030 R11: fffffbfff598d206 R12: ffffffffb0007c80
R13: 0000000000000005 R14: ffffffffb0007c85 R15: ffffffffb0007c80
 ? kasan_check_range+0x1c/0x1d0
 ? kasan_check_range+0x20/0x1d0
 ? kasan_check_range+0x1c/0x1d0
 apply_alternatives+0x79e/0x81d
 ? text_poke_early+0x9e/0x9e
 ? xas_clear_mark+0x1df/0x270
 ? apply_retpolines+0x4e4/0x535
 ? apply_alternatives+0x81d/0x81d
 ? delay_halt+0x31/0x60
 ? delay_halt+0x40/0x60
 ? delay_halt+0x36/0x60
 ? optimize_nops+0x225/0x225
 alternative_instructions+0x43/0x11a
 check_bugs+0x14fb/0x15b5
 ? l1tf_cmdline+0x10c/0x10c
 ? do_raw_spin_unlock+0x4f/0x250
 ? quirk_disable_msi.part.0+0x72/0x73
 ? poking_init+0x350/0x37f
 ? parse_direct_gbpages_off+0xd/0xd
 ? rcu_read_lock_bh_held+0xc0/0xc0
 start_kernel+0x38c/0x3bb
 secondary_startup_64_no_verify+0xe0/0xeb
 </TASK>

The buggy address belongs to the physical page:
page:ffd4000000d38e00 refcount:1 mapcount:0 mapping:0000000000000000
index:0x0 pfn:0x34e38
flags: 0x100000000001000(reserved|node=0|zone=1)
raw: 0100000000001000 ffd4000000d38e08 ffd4000000d38e08 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ff11000034e38a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ff11000034e38a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ff11000034e38b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                            ^
 ff11000034e38b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ff11000034e38c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
Disabling lock debugging due to kernel taint
debug: unmapping init [mem 0xffffffffb12b8000-0xffffffffb12c2fff]
smpboot: CPU0: Intel(R) Xeon(R) Platinum 8358 CPU @ 2.60GHz (family:
0x6, model: 0x6a, stepping: 0x6)

I'll try to get more details (boot options, configs, full logs, etc.), I
just wanted to give a heads up in case anything sticks out.


Vegard