linux-hardening - [PATCH] brcmfmac: replace deprecated strncpy with strscpy

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Message-ID: <20231016-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmfmac-cfg80211-c-v1-1-4234807ca07e@google.com>
Date: Mon, 16 Oct 2023 20:48:35 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Arend van Spriel <aspriel@...il.com>, Franky Lin <franky.lin@...adcom.com>, 
	Hante Meuleman <hante.meuleman@...adcom.com>, Kalle Valo <kvalo@...nel.org>
Cc: linux-wireless@...r.kernel.org, brcm80211-dev-list.pdl@...adcom.com, 
	SHA-cyfmac-dev-list@...ineon.com, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] brcmfmac: replace deprecated strncpy with strscpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect ifp->ndev->name to be NUL-terminated based on its use in
format strings within core.c:
via brcmf_ifname() ->
67 |       char *brcmf_ifname(struct brcmf_if *ifp)
68 |       {
69 |       	if (!ifp)
70 |       		return "<if_null>";
71 |
72 |       	if (ifp->ndev)
73 |       		return ifp->ndev->name;
74 |
75 |       	return "<if_none>";
76 |       }
...
288 |       static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *skb,
289 |       					   struct net_device *ndev) {
...
330 |       brcmf_dbg(INFO, "%s: insufficient headroom (%d)\n",
331 |                 brcmf_ifname(ifp), head_delta);
...
336 |       bphy_err(drvr, "%s: failed to expand headroom\n",
337 |                brcmf_ifname(ifp));

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
index 2a90bb24ba77..7daa418df877 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
@@ -866,7 +866,7 @@ struct wireless_dev *brcmf_apsta_add_vif(struct wiphy *wiphy, const char *name,
 		goto fail;
 	}
 
-	strncpy(ifp->ndev->name, name, sizeof(ifp->ndev->name) - 1);
+	strscpy(ifp->ndev->name, name, sizeof(ifp->ndev->name));
 	err = brcmf_net_attach(ifp, true);
 	if (err) {
 		bphy_err(drvr, "Registering netdevice failed\n");

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231016-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmfmac-cfg80211-c-a20108421685

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