linux-hardening - [PATCH v3 1/2] wifi: brcm80211: replace deprecated strncpy with strscpy

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Message-ID: <20231017-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmfmac-cfg80211-c-v3-1-af780d74ae38@google.com>
Date: Tue, 17 Oct 2023 20:11:28 +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 v3 1/2] wifi: brcm80211: replace deprecated strncpy with strscpy

Let's move away from using strncpy and instead favor a less ambiguous
and more robust interface.

For ifp->ndev->name, we expect ifp->ndev->name to be NUL-terminated based
on its use in format strings within core.c:
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));

For di->name, we expect di->name to be NUL-terminated based on its usage
with format strings:
|       brcms_dbg_dma(di->core,
|                     "%s: DMA64 tx doesn't have AE set\n",
|                     di->name);

Looking at its allocation we can see that it is already zero-allocated
which means NUL-padding is not required:
|       di = kzalloc(sizeof(struct dma_info), GFP_ATOMIC);

For wlc->modulecb[i].name, we expect each name in wlc->modulecb to be
NUL-terminated based on their usage with strcmp():
|       if (!strcmp(wlc->modulecb[i].name, name) &&

NUL-padding is not required as wlc is zero-allocated in:
brcms_c_attach_malloc() ->
|       wlc = kzalloc(sizeof(struct brcms_c_info), GFP_ATOMIC);

For all these cases, a suitable replacement is `strscpy` due to the fact
that it guarantees NUL-termination on the destination buffer without
unnecessarily NUL-padding.

Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 2 +-
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c      | 2 +-
 drivers/net/wireless/broadcom/brcm80211/brcmsmac/dma.c      | 3 +--
 drivers/net/wireless/broadcom/brcm80211/brcmsmac/main.c     | 4 ++--
 4 files changed, 5 insertions(+), 6 deletions(-)

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");
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
index d4492d02e4ea..6e0c90f4718b 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
@@ -2334,7 +2334,7 @@ struct wireless_dev *brcmf_p2p_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));
 	ifp->ndev->name_assign_type = name_assign_type;
 	err = brcmf_net_attach(ifp, true);
 	if (err) {
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmsmac/dma.c b/drivers/net/wireless/broadcom/brcm80211/brcmsmac/dma.c
index b7df576bb84d..3d5c1ef8f7f2 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmsmac/dma.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmsmac/dma.c
@@ -584,8 +584,7 @@ struct dma_pub *dma_attach(char *name, struct brcms_c_info *wlc,
 		      rxextheadroom, nrxpost, rxoffset, txregbase, rxregbase);
 
 	/* make a private copy of our callers name */
-	strncpy(di->name, name, MAXNAMEL);
-	di->name[MAXNAMEL - 1] = '\0';
+	strscpy(di->name, name, sizeof(di->name));
 
 	di->dmadev = core->dma_dev;
 
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmsmac/main.c b/drivers/net/wireless/broadcom/brcm80211/brcmsmac/main.c
index b3663c5ef382..34460b5815d0 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmsmac/main.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmsmac/main.c
@@ -5551,8 +5551,8 @@ int brcms_c_module_register(struct brcms_pub *pub,
 	/* find an empty entry and just add, no duplication check! */
 	for (i = 0; i < BRCMS_MAXMODULES; i++) {
 		if (wlc->modulecb[i].name[0] == '\0') {
-			strncpy(wlc->modulecb[i].name, name,
-				sizeof(wlc->modulecb[i].name) - 1);
+			strscpy(wlc->modulecb[i].name, name,
+				sizeof(wlc->modulecb[i].name));
 			wlc->modulecb[i].hdl = hdl;
 			wlc->modulecb[i].down_fn = d_fn;
 			return 0;

-- 
2.42.0.655.g421f12c284-goog