linux-kernel - Re: x86: potential ioremap() issues

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Date:	Fri, 29 Feb 2008 23:04:58 +0100
From:	"Oliver Pinter" <oliver.pntr@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Jan Beulich" <jbeulich@...ell.com>, linux-kernel@...r.kernel.org,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Arjan van de Ven" <arjan@...radead.org>
Subject: Re: x86: potential ioremap() issues

Hi Ingo!

this patch is needed for 2.6.22 kernel? I see, this code in
arch/x86_64/mm/ioremap.c

/* a kérdés az, hogy ezt a patchet backportoljam 2.6.22 alá vagy ne?
x86_64 alatt megtaláltam a cserélendő kódrészt...
 * köszönöm a választ
 */
On 2/28/08, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Jan Beulich <jbeulich@...ell.com> wrote:
>
> > Ingo,
> >
> > with the new ioremap() implementation I see a couple of (potential)
> > issues:
> > - When ioremap_page_range() fails, remove_vm_area() is used rather
> > than vunmap() - I think this will cause a 'struct vm_struct' leak.
>
> indeed, good catch - could you check whether the patch below fixes this?
> I also pushed this out into x86.git#testing, which you can pick up via:
>
> http://people.redhat.com/mingo/x86.git/README
>
> > - While ioremap() continues to happily map RAM pages (with a bogus
> > [see below] WARN_ON_ONCE()), cacheability of the memory is not
> > being restored in iounmap().
>
> correct - these are never supposed to be 'true', generally allocated RAM
> pages - or like we do with AGP where the pages are exclusively owned we
> restore their cacheability explicitly.
>
> > - The check for RAM pages (except for the WARN_ON_ONCE())
> > continues to be applied only to lowmem pages.
>
> yes, the biggest constraint from ioremap comes when it applies to pages
> that are mapped by the kernel. But i guess we could extend this to all
> things RAM ... the second patch below does this. What do you think? I've
> queued this up in x86.git#testing as well.
>
> > - The WARN_ON_ONCE() itself is applied to the pfn after the
> > preceding loop finished, i.e. to a pfn that doesn't actually participate
> > in the operation. Shouldn't it be moved inside the loop?
>
> i removed the WARN_ON_ONCE() from x86.git a few days ago, it's lined up
> for the next push.
>
> Ingo
>
> --------------------->
> Subject: x86: fix leak un ioremap_page_range() failure
> From: Ingo Molnar <mingo@...e.hu>
> Date: Thu Feb 28 14:02:08 CET 2008
>
> Jan Beulich noticed that if a driver's ioremap() fails (say due to -ENOMEM)
> then we might leak the struct vm_area - free it properly.
>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
> arch/x86/mm/ioremap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-x86.q/arch/x86/mm/ioremap.c
> ===================================================================
> --- linux-x86.q.orig/arch/x86/mm/ioremap.c
> +++ linux-x86.q/arch/x86/mm/ioremap.c
> @@ -179,7 +179,7 @@ static void __iomem *__ioremap(unsigned
> area->phys_addr = phys_addr;
> vaddr = (unsigned long) area->addr;
> if (ioremap_page_range(vaddr, vaddr + size, phys_addr, prot)) {
> -	remove_vm_area((void *)(vaddr & PAGE_MASK));
> +	free_vm_area(area);
> return NULL;
> }
>
> ------------------->
> Subject: x86: ioremap(), extend check to all RAM pages
> From: Ingo Molnar <mingo@...e.hu>
> Date: Thu Feb 28 14:10:49 CET 2008
>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
> arch/x86/mm/ioremap.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> Index: linux-x86.q/arch/x86/mm/ioremap.c
> ===================================================================
> --- linux-x86.q.orig/arch/x86/mm/ioremap.c
> +++ linux-x86.q/arch/x86/mm/ioremap.c
> @@ -146,8 +146,9 @@ static void __iomem *__ioremap(unsigned
> /*
> * Don't allow anybody to remap normal RAM that we're using..
> */
> -	for (pfn = phys_addr >> PAGE_SHIFT; pfn < max_pfn_mapped &&
> -	(pfn << PAGE_SHIFT) < last_addr; pfn++) {
> +	for (pfn = phys_addr >> PAGE_SHIFT;
> +	(pfn << PAGE_SHIFT) < last_addr; pfn++) {
> +
> if (page_is_ram(pfn) && pfn_valid(pfn) &&
> !PageReserved(pfn_to_page(pfn)))
> return NULL;
> --
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--
Thanks,
Oliver