Messages in this thread | | | Date | Fri, 22 Apr 2016 11:38:31 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: Fix incorrect pfn passed to untrack_pfn in remap_pfn_range |
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On Fri, 22 Apr 2016 18:31:28 +0800 Yongji Xie <xyjxie@linux.vnet.ibm.com> wrote:
> We used generic hooks in remap_pfn_range to help archs to > track pfnmap regions. The code is something like: > > int remap_pfn_range() > { > ... > track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size)); > ... > pfn -= addr >> PAGE_SHIFT; > ... > untrack_pfn(vma, pfn, PAGE_ALIGN(size)); > ... > } > > Here we can easily find the pfn is changed but not recovered > before untrack_pfn() is called. That's incorrect.
What are the runtime effects of this bug?
> --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1755,6 +1755,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, > break; > } while (pgd++, addr = next, addr != end); > > + pfn += (end - PAGE_ALIGN(size)) >> PAGE_SHIFT; > if (err) > untrack_pfn(vma, pfn, PAGE_ALIGN(size));
I'm having trouble understanding this. Wouldn't it be better to simply save the track_pfn_remap() call's `pfn' arg in a new local variable?
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