linux-hardening - [PATCH v2] wifi: ath10k: replace deprecated strncpy with memcpy

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Message-ID: <20231024-strncpy-drivers-net-wireless-ath-ath10k-mac-c-v2-1-4c1f4cd4b4df@google.com>
Date: Tue, 24 Oct 2023 17:42:16 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Kalle Valo <kvalo@...nel.org>, Jeff Johnson <quic_jjohnson@...cinc.com>
Cc: ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v2] wifi: ath10k: replace deprecated strncpy with memcpy

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@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
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@google.com
---
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);
 		}
 	}
 

---
base-commit: d88520ad73b79e71e3ddf08de335b8520ae41c5c
change-id: 20231013-strncpy-drivers-net-wireless-ath-ath10k-mac-c-c73a55666e6a

Best regards,
--
Justin Stitt <justinstitt@...gle.com>