Re: [PATCH 1/2] x86: ioremap: fix wrong physical address handling

[Kenji Kaneshige]

(2010/06/18 20:07), Jeremy Fitzhardinge wrote:
> On 06/18/2010 04:22 AM, Kenji Kaneshige wrote:
> > Current x86 ioremap() doesn't handle physical address higher than
> > 32-bit properly in X86_32 PAE mode. When physical address higher than
> > 32-bit is passed to ioremap(), higher 32-bits in physical address is
> > cleared wrongly. Due to this bug, ioremap() can map wrong address to
> > linear address space.
> >
> > In my case, 64-bit MMIO region was assigned to a PCI device (ioat
> > device) on my system. Because of the ioremap()'s bug, wrong physical
> > address (instead of MMIO region) was mapped to linear address space.
> > Because of this, loading ioatdma driver caused unexpected behavior
> > (kernel panic, kernel hangup, ...).
> >
> > Signed-off-by: Kenji Kaneshige<kaneshige.kenji@xxxxxxxxxxxxxx>
> >
> > ---
> >   arch/x86/mm/ioremap.c   |   12 +++++-------
> >   include/linux/io.h      |    4 ++--
> >   include/linux/vmalloc.h |    2 +-
> >   lib/ioremap.c           |   10 +++++-----
> >   mm/vmalloc.c            |    2 +-
> >   5 files changed, 14 insertions(+), 16 deletions(-)
> >
> > Index: linux-2.6.34/arch/x86/mm/ioremap.c
> > ===================================================================
> > --- linux-2.6.34.orig/arch/x86/mm/ioremap.c
> > +++ linux-2.6.34/arch/x86/mm/ioremap.c
> > @@ -62,8 +62,8 @@ int ioremap_change_attr(unsigned long va
> >   static void __iomem *__ioremap_caller(resource_size_t phys_addr,
> >   		unsigned long size, unsigned long prot_val, void *caller)
> >   {
> > -	unsigned long pfn, offset, vaddr;
> > -	resource_size_t last_addr;
> > +	unsigned long offset, vaddr;
> > +	resource_size_t pfn, last_pfn, last_addr;
>
> Why is pfn resource_size_t here? Is it to avoid casting, or does it
> actually need to hold more than 32 bits? I don't see any use of pfn
> aside from the page_is_ram loop, and I don't think that can go beyond 32
> bits. If you're worried about boundary conditions at the 2^44 limit,
> then you can make last_pfn inclusive, or compute num_pages and use that
> for the loop condition.

The reason I changed here was phys_addr might be higher than 2^44. After
the discussion, I realized there would probably be many other codes that
cannot handle more than 32-bits pfn, and this would cause problems even
if I changed ioremap() to be able to handle more than 32-bits pfn. So I
decided to focus on making 44-bits physical address work properly this
time. But, I didn't find any reason to make it go back to unsigned long.
So I still make it resource_size_t even in v.3. Is there any problem on
this change? And I don't understand why pfn can't go beyond 32-bits.
Could you tell me why?


> >   	const resource_size_t unaligned_phys_addr = phys_addr;
> >   	const unsigned long unaligned_size = size;
> >   	struct vm_struct *area;
> > @@ -100,10 +100,8 @@ static void __iomem *__ioremap_caller(re
> >   	/*
> >   	 * Don't allow anybody to remap normal RAM that we're using..
> >   	 */
> > -	for (pfn = phys_addr>>  PAGE_SHIFT;
> > -				(pfn<<  PAGE_SHIFT)<  (last_addr&  PAGE_MASK);
> > -				pfn++) {
> > -
> > +	last_pfn = last_addr>>  PAGE_SHIFT;
>
> If last_addr can be non-page aligned, should it be rounding up to the
> next pfn rather than rounding down? Ah, looks like you fix it in the
> second patch.

Yes, I fixed it in the [PATCH 2/2].

Thanks,
Kenji Kaneshige


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