Re: [giflib-devel] [PATCH] lib/dgif_lib.c: Initialize Private->RunningBits

[Eric S. R. <es...@th...>]

Simon Thelen <fo...@c-...>:
> Hello,
> 
> When opening a gif file using giflib the RunningBits member of
> GifFilePrivateType is never initialized before access in
> DGifSetupDecompress (called from DGifGetImageDesc) causing the function
> to occasionally set GifFile->Error = D_GIF_ERR_READ_FAILED and return
> GIF_ERROR even though no actual error occurred.
> 
> I've attached a patch that initializes RunningBits to 0 in
> DGifOpenFileHandle, but it might be safer to memset Private to 0 after
> allocating with malloc as there might other variables that are accessed
> without initialization that I haven't hit.
> 
> Since I am not currently subscribed to the mailing list, please CC me in
> replies to this mail (though I will try and check the mailing list
> archives periodically).
> 
> -- 
> Simon Thelen

> --- lib/dgif_lib.c.orig	2016-01-16 22:04:46.645036386 +0100
> +++ lib/dgif_lib.c	2016-01-16 22:05:37.752384125 +0100
> @@ -109,6 +109,7 @@
>      Private->File = f;
>      Private->FileState = FILE_STATE_READ;
>      Private->Read = NULL;        /* don't use alternate input method (TVT) */
> +    Private->RunningBits = 0;    /* Make sure to initialize RunningBits */
>      GifFile->UserData = NULL;    /* TVT */
>      /*@=mustfreeonly@*/
>  

I think the memset is a better idea, and have pushed that change.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>