On Thu, Oct 05, 2023 at 12:30:18AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous
> interfaces.
>
> Let's opt for memcpy as we are copying strings into slices of length
> `ETH_GSTRING_LEN` within the `data` buffer. Other similar get_strings()
> implementations [2] [3] use memcpy().
>
> Link:
> https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> [1]
> Link:
> https://elixir.bootlin.com/linux/v6.3/source/drivers/infiniband/ulp/opa_vnic/opa_vnic_ethtool.c#L167
> [2]
> Link:
> https://elixir.bootlin.com/linux/v6.3/source/drivers/infiniband/ulp/ipoib/ipoib_ethtool.c#L137
> [3]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinst...@google.com>
> ---
> Note: build-tested only.
> ---
> drivers/net/dsa/lan9303-core.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/dsa/lan9303-core.c b/drivers/net/dsa/lan9303-core.c
> index ee67adeb2cdb..665d69384b62 100644
> --- a/drivers/net/dsa/lan9303-core.c
> +++ b/drivers/net/dsa/lan9303-core.c
> @@ -1013,8 +1013,8 @@ static void lan9303_get_strings(struct dsa_switch *ds,
> int port,
> return;
>
> for (u = 0; u < ARRAY_SIZE(lan9303_mib); u++) {
> - strncpy(data + u * ETH_GSTRING_LEN, lan9303_mib[u].name,
> - ETH_GSTRING_LEN);
> + memcpy(data + u * ETH_GSTRING_LEN, lan9303_mib[u].name,
> + ETH_GSTRING_LEN);
This won't work because lan9303_mib entries aren't ETH_GSTRING_LEN-long
strings; they're string pointers:
static const struct lan9303_mib_desc lan9303_mib[] = {
{ .offset = LAN9303_MAC_RX_BRDCST_CNT_0, .name = "RxBroad", },
So this really does need a strcpy-family function.
And, I think the vnic_gstrings_stats and ipoib_gstrings_stats examples
are actually buggy -- they're copying junk into userspace...
I am reminded of this patch, which correctly uses strscpy_pad():
https://lore.kernel.org/lkml/20230718-net-dsa-strncpy-v1-1-e84664747...@google.com/
I think you want to do the same here, and use strscpy_pad(). And perhaps
send some fixes for the other memcpy() users?
(Have I mentioned I really dislike the get_strings() API?)
-Kees
--
Kees Cook
