Re: [PATCH 3/3] depmod: fix string overflow

From: Lucas De Marchi <lucas.de.marchi@gmail.com>
To: linux-modules <linux-modules@vger.kernel.org>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Subject: Re: [PATCH 3/3] depmod: fix string overflow
Date: Sat, 13 Aug 2016 17:31:50 -0300	[thread overview]
Message-ID: <CAKi4VALH8cJEXnYsMVA99+JF13HAyX0AKd0n8qvkfX0sC5Ehig@mail.gmail.com> (raw)
In-Reply-To: <1470854233-19810-3-git-send-email-lucas.de.marchi@gmail.com>

On Wed, Aug 10, 2016 at 3:37 PM, Lucas De Marchi
<lucas.de.marchi@gmail.com> wrote:
> From: Lucas De Marchi <lucas.demarchi@intel.com>
>
> Use scratchbuf to fix issue with strcpy that may overflow the buffer we
> declared in the stack.
> ---
>  tools/depmod.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/tools/depmod.c b/tools/depmod.c
> index a2e07c1..be9e001 100644
> --- a/tools/depmod.c
> +++ b/tools/depmod.c
> @@ -35,6 +35,7 @@
>  #include <shared/hash.h>
>  #include <shared/macro.h>
>  #include <shared/util.h>
> +#include <shared/scratchbuf.h>
>
>  #include <libkmod/libkmod.h>
>
> @@ -1920,6 +1921,7 @@ static int output_symbols_bin(struct depmod *depmod, FILE *out)
>  {
>         struct index_node *idx;
>         char alias[1024];
> +       struct scratchbuf salias;
>         size_t baselen = sizeof("symbol:") - 1;
>         struct hash_iter iter;
>         const void *v;
> @@ -1932,16 +1934,21 @@ static int output_symbols_bin(struct depmod *depmod, FILE *out)
>                 return -ENOMEM;
>
>         memcpy(alias, "symbol:", baselen);
> +       scratchbuf_init(&salias, alias, sizeof(alias));
> +
>         hash_iter_init(depmod->symbols, &iter);
>
>         while (hash_iter_next(&iter, NULL, &v)) {
>                 int duplicate;
>                 const struct symbol *sym = v;
> +               size_t len;
>
>                 if (sym->owner == NULL)
>                         continue;
>
> -               strcpy(alias + baselen, sym->name);
> +               len = strlen(sym->name);
> +               scratchbuf_alloc(&salias, baselen + len + 1);

err... the whole point of scratchbuf was to be able to increase the
buffer size and check for errors. Here I forgot to check them.

Lucas De Marchi