[PATCH 3/3] vm: fix vm_pgoff wrap in upward expansion - CVE-2011-2496

[Seth Forshee]

On Tue, Oct 11, 2011 at 05:39:21PM +0200, Paolo Pisati wrote:
> Commit a626ca6a6564 ("vm: fix vm_pgoff wrap in stack expansion") fixed
> the case of an expanding mapping causing vm_pgoff wrapping when you had
> downward stack expansion.  But there was another case where IA64 and
> PA-RISC expand mappings: upward expansion.
> 
> This fixes that case too.
> 
> Signed-off-by: Hugh Dickins <hughd at google.com>
> Cc: stable at kernel.org
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> 
> CVE-2011-2496
> 
> BugLink: http://bugs.launchpad.net/bugs/869243
> 
> commit upstream a626ca6a656450e9f4df91d0dda238fff23285f4

This is incorrect, it's the same upstream commit that patch 2 refers to.

You're also missing the From line to maintain correct authorship
information.

> 
> Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
> ---
>  mm/mmap.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 1508d86..027108e 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1735,9 +1735,12 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
>  		size = address - vma->vm_start;
>  		grow = (address - vma->vm_end) >> PAGE_SHIFT;
>  
> -		error = acct_stack_growth(vma, size, grow);
> -		if (!error)
> -			vma->vm_end = address;
> +		error = -ENOMEM;
> +		if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
> +			error = acct_stack_growth(vma, size, grow);
> +			if (!error)
> +				vma->vm_end = address;
> +		}
>  	}
>  	anon_vma_unlock(vma);
>  	return error;
> -- 
> 1.7.5.4
> 
> 
> -- 
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