On Tue, Dec 12, 2023 at 10:47 PM Kees Cook <keesc...@chromium.org> wrote:
>
> Since "dev_search_path" can technically be as large as PATH_MAX,
> there was a risk of truncation when copying it and a second string
> into "full_path" since it was also PATH_MAX sized. The W=1 builds were
> reporting this warning:
>
> drivers/block/rnbd/rnbd-srv.c: In function 'process_msg_open.isra':
> drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be
> truncated writing up to 254 bytes into a region of size between 0 and 4095
> [-Wformat-truncation=]
> 616 | snprintf(full_path, PATH_MAX, "%s/%s",
> | ^~
> In function 'rnbd_srv_get_full_path',
> inlined from 'process_msg_open.isra' at
> drivers/block/rnbd/rnbd-srv.c:721:14: drivers/block/rnbd/rnbd-srv.c:616:17:
> note: 'snprintf' output between 2 and 4351 bytes into a destination of size
> 4096
> 616 | snprintf(full_path, PATH_MAX, "%s/%s",
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 617 | dev_search_path, dev_name);
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> To fix this, unconditionally check for truncation (as was already done
> for the case where "%SESSNAME%" was present).
>
> Reported-by: kernel test robot <l...@intel.com>
> Closes:
> https://lore.kernel.org/oe-kbuild-all/202312100355.lhojpgky-...@intel.com/
> Cc: "Md. Haris Iqbal" <haris.iq...@ionos.com>
> Cc: Jack Wang <jinpu.w...@ionos.com>
> Cc: Jens Axboe <ax...@kernel.dk>
> Cc: linux-block@vger.kernel.org
> Signed-off-by: Kees Cook <keesc...@chromium.org>
lgtm.
Acked-by: Jack Wang <jinpu.w...@ionos.com>
> ---
> drivers/block/rnbd/rnbd-srv.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
> index 65de51f3dfd9..ab78eab97d98 100644
> --- a/drivers/block/rnbd/rnbd-srv.c
> +++ b/drivers/block/rnbd/rnbd-srv.c
> @@ -585,6 +585,7 @@ static char *rnbd_srv_get_full_path(struct
> rnbd_srv_session *srv_sess,
> {
> char *full_path;
> char *a, *b;
> + int len;
>
> full_path = kmalloc(PATH_MAX, GFP_KERNEL);
> if (!full_path)
> @@ -596,19 +597,19 @@ static char *rnbd_srv_get_full_path(struct
> rnbd_srv_session *srv_sess,
> */
> a = strnstr(dev_search_path, "%SESSNAME%", sizeof(dev_search_path));
> if (a) {
> - int len = a - dev_search_path;
> + len = a - dev_search_path;
>
> len = snprintf(full_path, PATH_MAX, "%.*s/%s/%s", len,
> dev_search_path, srv_sess->sessname, dev_name);
> - if (len >= PATH_MAX) {
> - pr_err("Too long path: %s, %s, %s\n",
> - dev_search_path, srv_sess->sessname, dev_name);
> - kfree(full_path);
> - return ERR_PTR(-EINVAL);
> - }
> } else {
> - snprintf(full_path, PATH_MAX, "%s/%s",
> - dev_search_path, dev_name);
> + len = snprintf(full_path, PATH_MAX, "%s/%s",
> + dev_search_path, dev_name);
> + }
> + if (len >= PATH_MAX) {
> + pr_err("Too long path: %s, %s, %s\n",
> + dev_search_path, srv_sess->sessname, dev_name);
> + kfree(full_path);
> + return ERR_PTR(-EINVAL);
> }
>
> /* eliminitate duplicated slashes */
> --
> 2.34.1
>
