Re: [PATCH] modpost: fix buffer overflow

[Sam Ravnborg <sam@ravnborg.org>]

On Wed, Mar 15, 2006 at 04:08:58PM +0100, Jiri Benc wrote:
> I got SIGABRT in modpost when compiling a module really deeply nested in
> a filesystem (path > 100 chars):
> 
> >   Building modules, stage 2.
> >   MODPOST
> > *** glibc detected *** scripts/mod/modpost: realloc(): invalid next size: 0x0809f588 ***
> > [...]
> 
> This patch fixes that problem.
> 
> Signed-off-by: Jiri Benc <jbenc@suse.cz>
> 
> --- linux-2.6.16-rc6.orig/scripts/mod/modpost.c
> +++ linux-2.6.16-rc6/scripts/mod/modpost.c
> @@ -553,7 +553,8 @@ void __attribute__((format(printf, 2, 3)
>  	va_start(ap, fmt);
>  	len = vsnprintf(tmp, SZ, fmt, ap);
>  	if (buf->size - buf->pos < len + 1) {
> -		buf->size += 128;
> +		while (buf->size - buf->pos < len + 1)
> +			buf->size += 128;
>  		buf->p = realloc(buf->p, buf->size);
>  	}
>  	strncpy(buf->p + buf->pos, tmp, len + 1);

Hi Jiri.

Can I ask you to make a new patch where you change buf_printf() to use
buf_write. And then change buf_write to allocate in chunks also.
This would be cleanest solution.

	Sam