Date:   Tue, 15 Aug 2017 22:45:00 +0800
From:   Ding Tianhong <dingtianhong@...wei.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>
CC:     <leedom@...lsio.com>, <ashok.raj@...el.com>, <bhelgaas@...gle.com>,
        <helgaas@...nel.org>, <werner@...lsio.com>, <ganeshgr@...lsio.com>,
        <asit.k.mallick@...el.com>, <patrick.j.cramer@...el.com>,
        <Suravee.Suthikulpanit@....com>, <Bob.Shaw@....com>,
        <l.stach@...gutronix.de>, <amira@...lanox.com>,
        <gabriele.paoloni@...wei.com>, <David.Laight@...lab.com>,
        <jeffrey.t.kirsher@...el.com>, <catalin.marinas@....com>,
        <will.deacon@....com>, <mark.rutland@....com>,
        <robin.murphy@....com>, <alexander.duyck@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>, <netdev@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>
Subject: Re: [PATCH v11 0/5] Add new PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag



On 2017/8/15 22:03, Eric Dumazet wrote:
> On Tue, 2017-08-15 at 06:58 -0700, Eric Dumazet wrote:
>> On Mon, 2017-08-14 at 22:15 -0700, David Miller wrote:
>>> From: Ding Tianhong <dingtianhong@...wei.com>
>>> Date: Tue, 15 Aug 2017 11:23:22 +0800
>>>
>>>> Some devices have problems with Transaction Layer Packets with the Relaxed
>>>> Ordering Attribute set.  This patch set adds a new PCIe Device Flag,
>>>> PCI_DEV_FLAGS_NO_RELAXED_ORDERING, a set of PCI Quirks to catch some known
>>>> devices with Relaxed Ordering issues, and a use of this new flag by the
>>>> cxgb4 driver to avoid using Relaxed Ordering with problematic Root Complex
>>>> Ports.
>>>  ...
>>>
>>> Series applied, thanks.
>>
>> I got a NULL deref in pci_find_pcie_root_port()
>>
> 
> This was :
> 
> [    4.241029] BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
> [    4.247001] IP: pci_find_pcie_root_port+0x62/0x80
> [    4.253011] PGD 0 
> [    4.253011] P4D 0 
> [    4.253011] 
> [    4.258013] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
> [    4.262015] Modules linked in:
> [    4.265005] CPU: 31 PID: 1 Comm: swapper/0 Not tainted 4.13.0-dbx-DEV #316
> [    4.271002] Hardware name: Intel RML,PCH/Iota_QC_19, BIOS 2.40.0 06/22/2016
> [    4.279002] task: ffffa2ee38cfa040 task.stack: ffffa51ec0004000
> [    4.285001] RIP: 0010:pci_find_pcie_root_port+0x62/0x80
> [    4.290012] RSP: 0000:ffffa51ec0007ab8 EFLAGS: 00010246
> [    4.295003] RAX: 0000000000000000 RBX: ffffa2ee36bae000 RCX: 0000000000000006
> [    4.303002] RDX: 000000000000081c RSI: ffffa2ee38cfa8c8 RDI: ffffa2ee36bae000
> [    4.310013] RBP: ffffa51ec0007b58 R08: 0000000000000001 R09: 0000000000000000
> [    4.317001] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa51ec0007ad0
> [    4.324005] R13: ffffa2ee36bae098 R14: 0000000000000002 R15: ffffa2ee37204818
> [    4.331002] FS:  0000000000000000(0000) GS:ffffa2ee3fcc0000(0000) knlGS:0000000000000000
> [    4.339002] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    4.345001] CR2: 0000000000000050 CR3: 000000401000f000 CR4: 00000000001406e0
> [    4.351002] Call Trace:
> [    4.354012]  ? pci_configure_device+0x19f/0x570
> [    4.359002]  ? pci_conf1_read+0xb8/0xf0
> [    4.363002]  ? raw_pci_read+0x23/0x40
> [    4.366011]  ? pci_read+0x2c/0x30
> [    4.370014]  ? pci_read_config_word+0x67/0x70
> [    4.374012]  pci_device_add+0x28/0x230
> [    4.378012]  ? pci_vpd_f0_read+0x50/0x80
> [    4.382014]  pci_scan_single_device+0x96/0xc0
> [    4.386012]  pci_scan_slot+0x79/0xf0
> [    4.389001]  pci_scan_child_bus+0x31/0x180
> [    4.394014]  acpi_pci_root_create+0x1c6/0x240
> [    4.398013]  pci_acpi_scan_root+0x15f/0x1b0
> [    4.402012]  acpi_pci_root_add+0x2e6/0x400
> [    4.406012]  ? acpi_evaluate_integer+0x37/0x60
> [    4.411002]  acpi_bus_attach+0xdf/0x200
> [    4.415002]  acpi_bus_attach+0x6a/0x200
> [    4.418014]  acpi_bus_attach+0x6a/0x200
> [    4.422013]  acpi_bus_scan+0x38/0x70
> [    4.426011]  acpi_scan_init+0x10c/0x271
> [    4.429001]  acpi_init+0x2fa/0x348
> [    4.433004]  ? acpi_sleep_proc_init+0x2d/0x2d
> [    4.437001]  do_one_initcall+0x43/0x169
> [    4.441001]  kernel_init_freeable+0x1d0/0x258
> [    4.445003]  ? rest_init+0xe0/0xe0
> [    4.449001]  kernel_init+0xe/0x150
> [    4.451002]  ret_from_fork+0x27/0x40
> [    4.457004] Code: 85 d2 74 27 80 7a 4a 00 74 21 48 89 d0 48 89 c2 f6 80 1b 09 00 00 10 74 07 48 8b 90 a0 0a 00 00 48 8b 52 10 48 83 7a 10 00 75 d0 <0f> b7 50 50 5d 81 e2 f0 00 00 00 83 fa 40 ba 00 00 00 00 48 0f 
> [    4.474012] RIP: pci_find_pcie_root_port+0x62/0x80 RSP: ffffa51ec0007ab8
> [    4.481004] CR2: 0000000000000050
> [    4.484001] ---[ end trace 6f9be6a057581199 ]---
> [    4.488001] Kernel panic - not syncing: Fatal exception
> [    4.494013] Rebooting in 10 seconds..
> [    4.494013] ACPI MEMORY or I/O RESET_REG.
> 
>>
>> This local hack seems to fix the issue.
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index af0cc3456dc1b48b1325c06c5edd2ca8cc22a640..cfd8eb5a3d0ba8347d44952ffab28d9c761044d3 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -522,7 +522,7 @@ struct pci_dev *pci_find_pcie_root_port(struct pci_dev *dev)
>>                 bridge = pci_upstream_bridge(bridge);
>>         }
>>  
>> -       if (pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT)
>> +       if (highest_pcie_bridge && pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT)
>>                 return NULL;
>>  
>>         return highest_pcie_bridge;
> 

It is very strange that I could not reproduce this problem on my server which is Xeon 2690v3,
but it is really a obviously issue when the dev could not find a upstream bridge in the
pci_find_pcie_root_port(), so the better way is just like your did in this patch. Thanks.

Regards
Tianhong

> 
> 
> .
> 

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