Re: [PATCH] libfdt: check for potential overrun in _fdt_splice()

[David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>]

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On Mon, Aug 10, 2015 at 11:39:02AM -0700, Bjorn Andersson wrote:
> From: Courtney Cavin <courtney.cavin-/MT0OVThwyLZJqsBc5GL+g@public.gmane.org>
> 
> Signed-off-by: Courtney Cavin <courtney.cavin-/MT0OVThwyLZJqsBc5GL+g@public.gmane.org>
> Signed-off-by: Bjorn Andersson <bjorn.andersson-/MT0OVThwyLZJqsBc5GL+g@public.gmane.org>


The logic looks ok, but this needs a commit message explaining the
details of what condition it is protecting against, and how it might
arise.

> ---
>  libfdt/fdt_rw.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/libfdt/fdt_rw.c b/libfdt/fdt_rw.c
> index 70adec6c371b..8be02b1f68f3 100644
> --- a/libfdt/fdt_rw.c
> +++ b/libfdt/fdt_rw.c
> @@ -101,6 +101,8 @@ static int _fdt_splice(void *fdt, void *splicepoint, int oldlen, int newlen)
>  
>  	if (((p + oldlen) < p) || ((p + oldlen) > end))
>  		return -FDT_ERR_BADOFFSET;
> +	if ((p < (char *)fdt) || ((end - oldlen + newlen) < (char *)fdt))
> +		return -FDT_ERR_BADOFFSET;
>  	if ((end - oldlen + newlen) > ((char *)fdt + fdt_totalsize(fdt)))
>  		return -FDT_ERR_NOSPACE;
>  	memmove(p + newlen, p + oldlen, end - p - oldlen);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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