Re: [PATCH v3 1/2] PCI: Avoid panic when PCI IO resource's size is not page aligned

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, May 29, 2018 at 08:18:18PM +0800, Yisheng Xie wrote:
> Zhou reported a bug on Hisilicon arm64 D06 platform with 64KB page size:
> 
>  [    2.470908] kernel BUG at lib/ioremap.c:72!
>  [    2.475079] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
>  [    2.480551] Modules linked in:
>  [    2.483594] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.16.0-rc7-00062-g0b41260-dirty #23
>  [    2.491756] Hardware name: Huawei D06/D06, BIOS Hisilicon D06 UEFI Nemo 2.0 RC0 - B120 03/23/2018
>  [    2.500614] pstate: 80c00009 (Nzcv daif +PAN +UAO)
>  [    2.505395] pc : ioremap_page_range+0x268/0x36c
>  [    2.509912] lr : pci_remap_iospace+0xe4/0x100
>  [...]
>  [    2.603733] Call trace:
>  [    2.606168]  ioremap_page_range+0x268/0x36c
>  [    2.610337]  pci_remap_iospace+0xe4/0x100
>  [    2.614334]  acpi_pci_probe_root_resources+0x1d4/0x214
>  [    2.619460]  pci_acpi_root_prepare_resources+0x18/0xa8
>  [    2.624585]  acpi_pci_root_create+0x98/0x214
>  [    2.628843]  pci_acpi_scan_root+0x124/0x20c
>  [    2.633013]  acpi_pci_root_add+0x224/0x494
>  [    2.637096]  acpi_bus_attach+0xf8/0x200
>  [    2.640918]  acpi_bus_attach+0x98/0x200
>  [    2.644740]  acpi_bus_attach+0x98/0x200
>  [    2.648562]  acpi_bus_scan+0x48/0x9c
>  [    2.652125]  acpi_scan_init+0x104/0x268
>  [    2.655948]  acpi_init+0x308/0x374
>  [    2.659337]  do_one_initcall+0x48/0x14c
>  [    2.663160]  kernel_init_freeable+0x19c/0x250
>  [    2.667504]  kernel_init+0x10/0x100
>  [    2.670979]  ret_from_fork+0x10/0x18
> 
> The cause is the size of PCI IO resource is 32KB, which is 4K aligned but
> not 64KB aligned, however, ioremap_page_range() request the range as page
> aligned or it will trigger a BUG_ON() on ioremap_pte_range() it calls, as
> ioremap_pte_range increase the addr by PAGE_SIZE, which makes addr != end
> until trigger BUG_ON, if its incoming end is not page aligned. More detail
> trace is as following:
> 
>  ioremap_page_range
>  -> ioremap_p4d_range
>     -> ioremap_p4d_range
>        -> ioremap_pud_range
>           -> ioremap_pmd_range
>              -> ioremap_pte_range
> 
> This patch avoid panic by return -EINVAL if vaddr or resource size is not
> page aligned.
> 
> Reported-by: Zhou Wang <wangzhou1@hisilicon.com>
> Tested-by: Xiaojun Tan <tanxiaojun@huawei.com>
> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
> ---
> v3:
>  - pci_remap_iospace() sanitize its arguments instead - per Rafael
> 
> v2:
>  - Let the caller of ioremap_page_range() align the request by PAGE_SIZE - per Toshi
> 
>  drivers/pci/pci.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index dbfe7c4..0eb0381 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3544,6 +3544,9 @@ int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
>  	if (res->end > IO_SPACE_LIMIT)
>  		return -EINVAL;
>  
> +	if (!PAGE_ALIGNED(vaddr) || !PAGE_ALIGNED(resource_size(res)))
> +		return -EINVAL;

Most other callers of ioremap_page_range() are in the ioremap() path,
and they align phys_addr themselves.  In some cases that results in a
mapping that covers more than necessary.  For instance, see the
function comment at the x86 version of __ioremap_caller().

Is there any reason we couldn't similarly align vaddr and phys_addr
here?

The acpi_pci_probe_root_resources() path you mention above basically
ignores the errors you're returning.  Your patches will avoid the
panic, which is an improvement, but I/O port space will not work, and
I don't see anything that gives the user a hint about why not.

If we could align vaddr and phys_addr (and possibly map more than
necessary), I/O port space would still work.

>  	return ioremap_page_range(vaddr, vaddr + resource_size(res), phys_addr,
>  				  pgprot_device(PAGE_KERNEL));
>  #else
> -- 
> 1.7.12.4
> 
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