From tomas.kalibera at gmail.com  Fri May 19 19:07:31 2017
From: tomas.kalibera at gmail.com (Tomas Kalibera)
Date: Fri, 19 May 2017 19:07:31 +0200
Subject: [Rd] Null pointer dereference?
In-Reply-To: <CANn+0XObL+1EHdGCObmRzNMRLmutW8OrPjpAryfSLHOhbxpQ5Q@mail.gmail.com>
References: <CANn+0XObL+1EHdGCObmRzNMRLmutW8OrPjpAryfSLHOhbxpQ5Q@mail.gmail.com>
Message-ID: <821898ca-41d1-37dc-7edb-98a8847070b7@gmail.com>

Thanks, the tool is indeed right, this is a real error. Although it is 
unlikely to trigger and unlikely to cause new problems (R would fail 
soon anyway if out of memory), it is clearly something to be fixed and 
something to be classified as "true positive".

I've fixed this in a way that is consistent with coding style in that file.

Best,
Tomas

On 05/19/2017 06:12 PM, Zubin Mevawalla wrote:
> I was curious if this was a real null pointer dereference issue in
> R-devel/src/library/grDevices/src/devPS.c on line 1009?
>
> 1000: static type1fontinfo makeType1Font()
> 1001: {
> 1002:     type1fontinfo font = (Type1FontInfo *) malloc(sizeof(Type1FontInfo));
> 1003:     /*
> 1004:      * Initialise font->metrics.KernPairs to NULL
> 1005:      * so that we know NOT to free it if we fail to
> 1006:      * load this font and have to
> 1007:      * bail out and free this type1fontinfo
> 1008:      */
> 1009:     font->metrics.KernPairs = NULL;
> 1010:     if (!font)
> 1011: warning(_("failed to allocate Type 1 font info"));
> 1012:     return font;
> 1013: }
>
> `font` is conceivably null because there is a null check on line 1010,
> but is dereferenced on 1009.
>
> CodeAi, an automated repair tool being developed at Qbit logic,
> suggested an if-guard as a fix:
>
> @@ -1006,9 +1006,7 @@ static type1fontinfo makeType1Font()
>        * load this font and have to
>        * bail out and free this type1fontinfo
>        */
> -    if(font) {
> -        font->metrics.KernPairs = NULL;
> -    }
> +    font->metrics.KernPairs = NULL;
>       if (!font)
>          warning(_("failed to allocate Type 1 font info"));
>       return font;
>
> Could I submit this as a patch if it looks alright?
>
> Thanks so much,
>
> Zubin
>
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[Rd] Null pointer dereference?
Tomas Kalibera