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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id k11-20020a170902694b00b001b016313b1dsm11240816plt.86.2023.10.26.10.20.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Oct 2023 10:20:55 -0700 (PDT) Date: Thu, 26 Oct 2023 10:20:55 -0700 From: Kees Cook To: Justin Stitt Cc: Arend van Spriel , Franky Lin , Hante Meuleman , Kalle Valo , linux-wireless@vger.kernel.org, brcm80211-dev-list.pdl@broadcom.com, SHA-cyfmac-dev-list@infineon.com, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v3 1/2] wifi: brcm80211: replace deprecated strncpy with strscpy Message-ID: <202310261020.2D4DB7177@keescook> References: <20231017-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmfmac-cfg80211-c-v3-0-af780d74ae38@google.com> <20231017-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmfmac-cfg80211-c-v3-1-af780d74ae38@google.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231017-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmfmac-cfg80211-c-v3-1-af780d74ae38@google.com> On Tue, Oct 17, 2023 at 08:11:28PM +0000, Justin Stitt wrote: > 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 ""; > 71 | > 72 | if (ifp->ndev) > 73 | return ifp->ndev->name; > 74 | > 75 | return ""; > 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 Good; this looks like standard direct replacements. Reviewed-by: Kees Cook -- Kees Cook