On 10/24/2023 2:34 PM, Kees Cook wrote:
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?
yes, it is safe, and consistent with other uses of this field as noted
in the commit description.
