linux-kernel - Re: [RFC PATCH 1/2] resource: Request IO port regions from children of ioport

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Date:   Thu, 14 Mar 2019 17:39:12 +0000
From:   John Garry <john.garry@...wei.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     <jdelvare@...e.com>, <bhelgaas@...gle.com>, <rafael@...nel.org>,
        <arnd@...db.de>, <lorenzo.pieralisi@....com>, <bp@...e.de>,
        <linux-hwmon@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <wangkefeng.wang@...wei.com>,
        <linuxarm@...wei.com>
Subject: Re: [RFC PATCH 1/2] resource: Request IO port regions from children
 of ioport_resource

On 14/03/2019 17:12, Guenter Roeck wrote:
> On Fri, Mar 15, 2019 at 12:55:15AM +0800, John Garry wrote:
>> Currently when we request an IO port region, the request is made directly
>> to the top resource, ioport_resource.
>>
>> There is an issue here, in that drivers may request an IO port region even
>> if the IO port region has not even been mapped in (in pci_remap_iospace()).
>>
>> This may lead to crashes when the PCI host has not enumerated prior to
>> accessing the IO port region, as below:
>>
>> root@(none)$ insmod f71805f.ko
>> [   32.264016] Unable to handle kernel paging request at virtual address ffff7dfffee0002e
>> [   32.279936] Mem abort info:
>> [   32.285536]   ESR = 0x96000046
>> [   32.291657]   Exception class = DABT (current EL), IL = 32 bits
>> [   32.303542]   SET = 0, FnV = 0
>> [   32.309661]   EA = 0, S1PTW = 0
>> [   32.315957] Data abort info:
>> [   32.321728]   ISV = 0, ISS = 0x00000046
>> [   32.329420]   CM = 0, WnR = 1
>> [   32.335367] swapper pgtable: 4k pages, 48-bit VAs, pgdp = (____ptrval____)
>> [   32.349174] [ffff7dfffee0002e] pgd=0000000001392003, pud=0000000001393003, pmd=0000000000000000
>> [   32.366652] Internal error: Oops: 96000046 [#1] PREEMPT SMP
>> [   32.377835] Modules linked in: f71805f(+)
>> [   32.385876] CPU: 4 PID: 2681 Comm: insmod Not tainted 5.0.0-00003-ga6247cc0f8f2 #52
>> [   32.401252] Hardware name: Huawei Taishan 2280 /D05, BIOS Hisilicon D05 IT21 Nemo 2.0 RC0 04/18/2018
>> [   32.419597] pstate: 80000005 (Nzcv daif -PAN -UAO)
>> [   32.429213] pc : logic_outb+0x54/0xb8
>> [   32.436556] lr : f71805f_find+0x2c/0x1b8 [f71805f]
>> [   32.446167] sp : ffff0000256bba90
>> [   32.452808] x29: ffff0000256bba90 x28: ffff000008b544d0
>> [   32.463468] x27: ffff0000256bbdf0 x26: 0000000000000100
>> [   32.474127] x25: 000000000000002c x24: ffff000011396000
>> [   32.484787] x23: ffff0000256bbb3e x22: ffff0000256bbb40
>> [   32.495446] x21: ffff000008b591b8 x20: 0000000000000087
>> [   32.506106] x19: 000000000000002e x18: ffffffffffffffff
>> [   32.516765] x17: 0000000000000000 x16: 0000000000000000
>> [   32.527424] x15: 0000000000000400 x14: 0000000000000400
>> [   32.538084] x13: 0000000000001832 x12: 0000000000000000
>> [   32.548743] x11: ffff801ffbf08ac0 x10: 0000801fead02000
>> [   32.559403] x9 : ffff801ffbffe840 x8 : 0000000000000001
>> [   32.570062] x7 : 0000000000210d00 x6 : 0000000000000000
>> [   32.580721] x5 : ffff801fb3eac380 x4 : ffff801ffbef4b20
>> [   32.591381] x3 : 0000000000ffbffe x2 : ffff0000256bbb40
>> [   32.602040] x1 : ffff7dfffee0002e x0 : ffff7dfffee00000
>> [   32.612701] Process insmod (pid: 2681, stack limit = 0x(____ptrval____))
>> [   32.626155] Call trace:
>> [   32.631050]  logic_outb+0x54/0xb8
>> [   32.637693]  f71805f_find+0x2c/0x1b8 [f71805f]
>> [   32.646607]  f71805f_init+0x38/0xe48 [f71805f]
>> [   32.655521]  do_one_initcall+0x5c/0x178
>> [   32.663212]  do_init_module+0x58/0x1b0
>> [   32.670728]  load_module+0x1dc8/0x2178
>> [   32.678243]  __se_sys_init_module+0x14c/0x1e8
>> [   32.686981]  __arm64_sys_init_module+0x18/0x20
>> [   32.695894]  el0_svc_common+0x60/0x100
>> [   32.703409]  el0_svc_handler+0x2c/0x80
>> [   32.710924]  el0_svc+0x8/0xc
>> [   32.716693] Code: d2bfdc00 f2cfbfe0 f2ffffe0 8b000021 (39000034)
>> [   32.728925] ---[ end trace ddb5e493ee686685 ]---
>> Segmentation fault
>> root@(none)$
>>
>> This issue was originally reported in [1].
>>
>> This patch changes the functionality of request_region() to request a
>> region of the direct children of the top ioport_resource.
>>
>> In this, if the IO port region has not been mapped for a particular IO
>> region, a suitable child region will not exist, and, as such,
>> request_region() calls will fail.
>>
>> A side note: there are many drivers in the kernel which fail to even call
>> request_region() prior to IO port accesses, and they also need to be fixed
>> (to call request_region() as appropriate).
>>

Hi Guenter,

>
> Isn't that orthogonal to this problem ?

Yes, it is really. I only added the f71805f driver fixup to illustrate 
the problem in resource.c and the potential system crash, and how this 
patch would fix it.

>
>> [1] https://www.spinics.net/lists/linux-pci/msg49821.html
>>
>> Signed-off-by: John Garry <john.garry@...wei.com>
>> ---
>>  include/linux/ioport.h |  6 +++++-
>>  kernel/resource.c      | 19 +++++++++++++++++++
>>  2 files changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
>> index da0ebaec25f0..cf40e1ed8211 100644
>> --- a/include/linux/ioport.h
>> +++ b/include/linux/ioport.h
>> @@ -217,7 +217,7 @@ static inline bool resource_contains(struct resource *r1, struct resource *r2)
>>
>>
>>  /* Convenience shorthand with allocation */
>> -#define request_region(start,n,name)		__request_region(&ioport_resource, (start), (n), (name), 0)
>> +#define request_region(start,n,name)		__request_region_from_children(&ioport_resource, (start), (n), (name), 0)
>>  #define request_muxed_region(start,n,name)	__request_region(&ioport_resource, (start), (n), (name), IORESOURCE_MUXED)
>>  #define __request_mem_region(start,n,name, excl) __request_region(&iomem_resource, (start), (n), (name), excl)
>>  #define request_mem_region(start,n,name) __request_region(&iomem_resource, (start), (n), (name), 0)
>
> I can't comment on the merits of the patch (though I am a bit concerned
> about its impact and potential source of regressions),but I don't really
> understand why it would only apply to request_region() and not to
> request_muxed_region(). Is this an oversight or on purpose ?

It's an oversight, which would be fixed.

Thanks,
John

>
> Guenter
>
> .
>