On Tue, Oct 24, 2023 at 05:42:16PM +0000, Justin Stitt wrote:
> strncpy() is deprecated [1] and we should prefer less ambiguous
> interfaces.
>
> In this case, arvif->u.ap.ssid has its length maintained by
> arvif->u.ap.ssid_len which indicates it may not need to be
> NUL-terminated. Make this explicit with __nonstring and use a plain old
> memcpy.
>
> This is also consistent with future copies into arvif->u.ap.ssid:
>
> if (changed & BSS_CHANGED_SSID &&
> vif->type == NL80211_IFTYPE_AP) {
> arvif->u.ap.ssid_len = vif->cfg.ssid_len;
> if (vif->cfg.ssid_len)
> memcpy(arvif->u.ap.ssid, vif->cfg.ssid,
> vif->cfg.ssid_len);
> arvif->u.ap.hidden_ssid = info->hidden_ssid;
> }
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@xxxxxxxxxxxxxxx
> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
> ---
> Changes in v2:
> - update subject to include wifi
> - prefer memcpy() over strtomem() (thanks Kalle, Jeff)
> - rebase onto 6.6-rc7 @d88520ad73b79e71
> - Link to v1: https://lore.kernel.org/r/20231013-strncpy-drivers-net-wireless-ath-ath10k-mac-c-v1-1-24e40201afa3@xxxxxxxxxx
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> drivers/net/wireless/ath/ath10k/core.h | 2 +-
> drivers/net/wireless/ath/ath10k/mac.c | 3 +--
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/core.h b/drivers/net/wireless/ath/ath10k/core.h
> index 4b5239de4018..ba9795a8378a 100644
> --- a/drivers/net/wireless/ath/ath10k/core.h
> +++ b/drivers/net/wireless/ath/ath10k/core.h
> @@ -607,7 +607,7 @@ struct ath10k_vif {
> u8 tim_bitmap[64];
> u8 tim_len;
> u32 ssid_len;
> - u8 ssid[IEEE80211_MAX_SSID_LEN];
> + u8 ssid[IEEE80211_MAX_SSID_LEN] __nonstring;
> bool hidden_ssid;
> /* P2P_IE with NoA attribute for P2P_GO case */
> u32 noa_len;
> diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
> index 03e7bc5b6c0b..f3f6deb354c6 100644
> --- a/drivers/net/wireless/ath/ath10k/mac.c
> +++ b/drivers/net/wireless/ath/ath10k/mac.c
> @@ -6125,9 +6125,8 @@ static void ath10k_bss_info_changed(struct ieee80211_hw *hw,
>
> if (ieee80211_vif_is_mesh(vif)) {
> /* mesh doesn't use SSID but firmware needs it */
> - strncpy(arvif->u.ap.ssid, "mesh",
> - sizeof(arvif->u.ap.ssid));
> arvif->u.ap.ssid_len = 4;
> + memcpy(arvif->u.ap.ssid, "mesh", arvif->u.ap.ssid_len);
This is a behavior change, isn't it? i.e. arvif->u.ap.ssid is no longer
zero-padded. Is this actually ok for the driver?
-Kees
--
Kees Cook
