Re: [PATCH] mm/migrate: check for null vma before dereferencing it

From	Andrew Morton <akpm@linux-foundation.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mm/migrate: check for null vma before dereferencing it
Date	2017-04-11 23:50 +0200
Message-ID	<tvbPH-471-1@gated-at.bofh.it> (permalink)
References	<tv3yN-77s-3@gated-at.bofh.it> <tvbwm-3ZY-17@gated-at.bofh.it> <tvbG1-43u-11@gated-at.bofh.it>
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On Tue, 11 Apr 2017 22:31:12 +0100 Colin Ian King <colin.king@canonical.com> wrote:

> On 11/04/17 22:26, Andrew Morton wrote:
> > On Tue, 11 Apr 2017 13:51:02 +0100 Colin King <colin.king@canonical.com> wrote:
> > 
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> check if vma is null before dereferencing it, this avoiding any
> >> potential null pointer dereferences on vma via the is_vm_hugetlb_page
> >> call or the direct vma->vm_flags reference.
> >>
> >> Detected with CoverityScan, CID#1427995 ("Dereference before null check")
> >>
> >> ...
> >>
> >> --- a/mm/migrate.c
> >> +++ b/mm/migrate.c
> >> @@ -2757,10 +2757,10 @@ int migrate_vma(const struct migrate_vma_ops *ops,
> >>  	/* Sanity check the arguments */
> >>  	start &= PAGE_MASK;
> >>  	end &= PAGE_MASK;
> >> -	if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL))
> >> -		return -EINVAL;
> >>  	if (!vma || !ops || !src || !dst || start >= end)
> >>  		return -EINVAL;
> >> +	if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL))
> >> +		return -EINVAL;
> >>  	if (start < vma->vm_start || start >= vma->vm_end)
> >>  		return -EINVAL;
> >>  	if (end <= vma->vm_start || end > vma->vm_end)
> > 
> > I don't know what kernel version this is against but I don't think it's
> > anything recent?
> 
> I should have said it was against linux-next

ah, it modifies an HMM patch which I dropped a couple of hours ago.  One
for Jerome, please.

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[PATCH] mm/migrate: check for null vma before dereferencing it Colin King <colin.king@canonical.com> - 2017-04-11 15:00 +0200
  Re: [PATCH] mm/migrate: check for null vma before dereferencing it Andrew Morton <akpm@linux-foundation.org> - 2017-04-11 23:30 +0200
    Re: [PATCH] mm/migrate: check for null vma before dereferencing it Colin Ian King <colin.king@canonical.com> - 2017-04-11 23:40 +0200
      Re: [PATCH] mm/migrate: check for null vma before dereferencing it Andrew Morton <akpm@linux-foundation.org> - 2017-04-11 23:50 +0200

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