Re: [RFC PATCH v5 1/2] dtc: protect against null pointer dereference in srcpos_string()

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

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On Wed, Sep 30, 2015 at 08:32:44PM -0700, Frank Rowand wrote:
> From: Frank Rowand <frank.rowand-/MT0OVThwyLZJqsBc5GL+g@public.gmane.org>
> 
> Check for NULL pos before dereferencing it in srcpos_string().
> 
> Signed-off-by: Frank Rowand <frank.rowand-/MT0OVThwyLZJqsBc5GL+g@public.gmane.org>
> ---
>  srcpos.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> Index: b/srcpos.c
> ===================================================================
> --- a/srcpos.c
> +++ b/srcpos.c
> @@ -272,7 +272,9 @@ srcpos_string(struct srcpos *pos)
>  		fname = pos->file->name;

Hmm.. looking at the existing code, it looks like the
	if (pos)
above should probably be
	if (pos->file)

It would be nice to fix that at the same time..

>  
> -	if (pos->first_line != pos->last_line)
> +	if (!pos)
> +		rc = asprintf(&pos_str, "%s:0", fname);

Because this really should go very first, before even setting fname.
"<no-file>:0" seems an odd way to display this, rather than just
"<no-location>", for example.

> +	else if (pos->first_line != pos->last_line)
>  		rc = asprintf(&pos_str, "%s:%d.%d-%d.%d", fname,
>  			      pos->first_line, pos->first_column,
>  			      pos->last_line, pos->last_column);

-- 
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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