Re: [PATCH v2 3/3] libsepol: assure string NUL-termination of ibdev_name

[Nicolas Iooss <nicolas.iooss@m4x.org>]

On Thu, Jul 1, 2021 at 8:07 PM Christian Göttsche
<cgzones@googlemail.com> wrote:
>
> Clang complains:
>
>     ibendport_record.c: In function ‘sepol_ibendport_get_ibdev_name’:
>     ibendport_record.c:169:2: error: ‘strncpy’ specified bound 64 equals destination size [-Werror=stringop-truncation]
>       169 |  strncpy(tmp_ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX);
>           |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     ibendport_record.c: In function ‘sepol_ibendport_set_ibdev_name’:
>     ibendport_record.c:189:2: error: ‘strncpy’ specified bound 64 equals destination size [-Werror=stringop-truncation]
>       189 |  strncpy(tmp, ibdev_name, IB_DEVICE_NAME_MAX);
>           |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> strncpy(3) does not NUL-terminate the destination if the source is of
> the same length or longer then the specified size.
> The source of these copies are retrieved from
> sepol_ibendport_alloc_ibdev_name(), which allocates a fixed amount of
> IB_DEVICE_NAME_MAX bytes.
> Reduce the size to copy by 1 of all memory regions allocated by
> sepol_ibendport_alloc_ibdev_name().
>
> Signed-off-by: Christian Göttsche <cgzones@googlemail.com>

Acked-by: Nicolas Iooss <nicolas.iooss@m4x.org>

Thanks,
Nicolas

> ---
> v2:
>   - use at all affected places as pointed out by James Carter
>
>  libsepol/src/ibendport_record.c | 8 ++++----
>  libsepol/src/ibendports.c       | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/libsepol/src/ibendport_record.c b/libsepol/src/ibendport_record.c
> index adf67161..1eb50914 100644
> --- a/libsepol/src/ibendport_record.c
> +++ b/libsepol/src/ibendport_record.c
> @@ -62,7 +62,7 @@ int sepol_ibendport_key_create(sepol_handle_t *handle,
>         if (sepol_ibendport_alloc_ibdev_name(handle, &tmp_key->ibdev_name) < 0)
>                 goto err;
>
> -       strncpy(tmp_key->ibdev_name, ibdev_name, IB_DEVICE_NAME_MAX);
> +       strncpy(tmp_key->ibdev_name, ibdev_name, IB_DEVICE_NAME_MAX - 1);
>         tmp_key->port = port;
>
>         *key_ptr = tmp_key;
> @@ -166,7 +166,7 @@ int sepol_ibendport_get_ibdev_name(sepol_handle_t *handle,
>         if (sepol_ibendport_alloc_ibdev_name(handle, &tmp_ibdev_name) < 0)
>                 goto err;
>
> -       strncpy(tmp_ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX);
> +       strncpy(tmp_ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX - 1);
>         *ibdev_name = tmp_ibdev_name;
>         return STATUS_SUCCESS;
>
> @@ -186,7 +186,7 @@ int sepol_ibendport_set_ibdev_name(sepol_handle_t *handle,
>         if (sepol_ibendport_alloc_ibdev_name(handle, &tmp) < 0)
>                 goto err;
>
> -       strncpy(tmp, ibdev_name, IB_DEVICE_NAME_MAX);
> +       strncpy(tmp, ibdev_name, IB_DEVICE_NAME_MAX - 1);
>         free(ibendport->ibdev_name);
>         ibendport->ibdev_name = tmp;
>         return STATUS_SUCCESS;
> @@ -230,7 +230,7 @@ int sepol_ibendport_clone(sepol_handle_t *handle,
>         if (sepol_ibendport_alloc_ibdev_name(handle, &new_ibendport->ibdev_name) < 0)
>                 goto omem;
>
> -       strncpy(new_ibendport->ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX);
> +       strncpy(new_ibendport->ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX - 1);
>         new_ibendport->port = ibendport->port;
>
>         if (ibendport->con &&
> diff --git a/libsepol/src/ibendports.c b/libsepol/src/ibendports.c
> index 6d56c9a1..ee5cb193 100644
> --- a/libsepol/src/ibendports.c
> +++ b/libsepol/src/ibendports.c
> @@ -34,7 +34,7 @@ static int ibendport_from_record(sepol_handle_t *handle,
>                                            &ibdev_name) < 0)
>                 goto err;
>
> -       strncpy(tmp_ibendport->u.ibendport.dev_name, ibdev_name, IB_DEVICE_NAME_MAX);
> +       strncpy(tmp_ibendport->u.ibendport.dev_name, ibdev_name, IB_DEVICE_NAME_MAX - 1);
>
>         free(ibdev_name);
>         ibdev_name = NULL;
> --
> 2.32.0
>