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Date: Wed, 14 Mar 2018 00:53:51 +0000
From: Sasha Levin <Alexander.Levin@...rosoft.com>
To: Pavel Tatashin <pasha.tatashin@...cle.com>
CC: "steven.sistare@...cle.com" <steven.sistare@...cle.com>,
"daniel.m.jordan@...cle.com" <daniel.m.jordan@...cle.com>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"mgorman@...hsingularity.net" <mgorman@...hsingularity.net>,
"mhocko@...e.com" <mhocko@...e.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"vbabka@...e.cz" <vbabka@...e.cz>,
"bharata@...ux.vnet.ibm.com" <bharata@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 1/2] mm: uninitialized struct page poisoning sanity
checking
On Tue, Mar 13, 2018 at 08:38:57PM -0400, Pavel Tatashin wrote:
>Hi Sasha,
>
>It seems the patch is doing the right thing, and it catches bugs. Here
>we access uninitialized struct page. The question is why this happens?
Not completely; note that we die on an invalid reference rather than
assertion failure.
>register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
> page_nid = get_nid_for_pfn(pfn);
>
>node id is stored in page flags, and since struct page is poisoned,
>and the pattern is recognized, the panic is triggered.
>
>Do you have config file? Also, instructions how to reproduce it?
Attached the config. It just happens on boot.
>Thank you,
>Pasha
>
>
>On Tue, Mar 13, 2018 at 7:43 PM, Sasha Levin
><Alexander.Levin@...rosoft.com> wrote:
>> On Wed, Jan 31, 2018 at 04:02:59PM -0500, Pavel Tatashin wrote:
>>>During boot we poison struct page memory in order to ensure that no one is
>>>accessing this memory until the struct pages are initialized in
>>>__init_single_page().
>>>
>>>This patch adds more scrutiny to this checking, by making sure that flags
>>>do not equal to poison pattern when the are accessed. The pattern is all
>>>ones.
>>>
>>>Since, node id is also stored in struct page, and may be accessed quiet
>>>early we add the enforcement into page_to_nid() function as well.
>>>
>>>Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
>>>---
>>
>> Hey Pasha,
>>
>> This patch is causing the following on boot:
>>
>> [ 1.253732] BUG: unable to handle kernel paging request at fffffffffffffffe
>> [ 1.254000] PGD 2284e19067 P4D 2284e19067 PUD 2284e1b067 PMD 0
>> [ 1.254000] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
>> [ 1.254000] Modules linked in:
>> [ 1.254000] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.16.0-rc5-next-20180313 #10
>> [ 1.254000] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090007 06/02/2017
>> [ 1.254000] RIP: 0010:__dump_page (??:?)
>> [ 1.254000] RSP: 0000:ffff881c63c17810 EFLAGS: 00010246
>> [ 1.254000] RAX: dffffc0000000000 RBX: ffffea0084000000 RCX: 1ffff1038c782f2b
>> [ 1.254000] RDX: 1fffffffffffffff RSI: ffffffff9e160640 RDI: ffffea0084000000
>> [ 1.254000] RBP: ffff881c63c17c00 R08: ffff8840107e8880 R09: ffffed0802167a4d
>> [ 1.254000] R10: 0000000000000001 R11: ffffed0802167a4c R12: 1ffff1038c782f07
>> [ 1.254000] R13: ffffea0084000020 R14: fffffffffffffffe R15: ffff881c63c17bd8
>> [ 1.254000] FS: 0000000000000000(0000) GS:ffff881c6ac00000(0000) knlGS:0000000000000000
>> [ 1.254000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 1.254000] CR2: fffffffffffffffe CR3: 0000002284e16000 CR4: 00000000003406e0
>> [ 1.254000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> [ 1.254000] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> [ 1.254000] Call Trace:
>> [ 1.254000] dump_page (/mm/debug.c:80)
>> [ 1.254000] get_nid_for_pfn (/./include/linux/mm.h:900 /drivers/base/node.c:396)
>> [ 1.254000] register_mem_sect_under_node (/drivers/base/node.c:438)
>> [ 1.254000] link_mem_sections (/drivers/base/node.c:517)
>> [ 1.254000] topology_init (/./include/linux/nodemask.h:271 /arch/x86/kernel/topology.c:164)
>> [ 1.254000] do_one_initcall (/init/main.c:835)
>> [ 1.254000] kernel_init_freeable (/init/main.c:901 /init/main.c:909 /init/main.c:927 /init/main.c:1076)
>> [ 1.254000] kernel_init (/init/main.c:1004)
>> [ 1.254000] ret_from_fork (/arch/x86/entry/entry_64.S:417)
>> [ 1.254000] Code: ff a8 01 4c 0f 44 f3 4d 85 f6 0f 84 31 0e 00 00 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 2d 11 00 00 <49> 83 3e ff 0f 84 a9 06 00 00 4d 8d b7 c0 fd ff ff 48 b8 00 00
>> All code
>> ========
>> 0: ff a8 01 4c 0f 44 ljmp *0x440f4c01(%rax)
>> 6: f3 4d 85 f6 repz test %r14,%r14
>> a: 0f 84 31 0e 00 00 je 0xe41
>> 10: 4c 89 f2 mov %r14,%rdx
>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
>> 1a: fc ff df
>> 1d: 48 c1 ea 03 shr $0x3,%rdx
>> 21: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
>> 25: 0f 85 2d 11 00 00 jne 0x1158
>> 2b:* 49 83 3e ff cmpq $0xffffffffffffffff,(%r14) <-- trapping instruction
>> 2f: 0f 84 a9 06 00 00 je 0x6de
>> 35: 4d 8d b7 c0 fd ff ff lea -0x240(%r15),%r14
>> 3c: 48 rex.W
>> 3d: b8 .byte 0xb8
>> ...
>>
>> Code starting with the faulting instruction
>> ===========================================
>> 0: 49 83 3e ff cmpq $0xffffffffffffffff,(%r14)
>> 4: 0f 84 a9 06 00 00 je 0x6b3
>> a: 4d 8d b7 c0 fd ff ff lea -0x240(%r15),%r14
>> 11: 48 rex.W
>> 12: b8 .byte 0xb8
>> ...
>> [ 1.254000] RIP: __dump_page+0x1c8/0x13c0 RSP: ffff881c63c17810 (/./include/asm-generic/sections.h:42)
>> [ 1.254000] CR2: fffffffffffffffe
>> [ 1.254000] ---[ end trace e643dfbc44b562ca ]---
>>
>> --
>>
>> Thanks,
>> Sasha
--
Thanks,
Sasha
Download attachment "config-sasha.gz" of type "application/gzip" (33407 bytes)
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