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Mon, 13 Apr 2026 02:30:55 -0700 (PDT) Received: from [192.168.88.32] ([216.128.11.125]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488d58a8438sm312055965e9.5.2026.04.13.02.30.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Apr 2026 02:30:54 -0700 (PDT) Message-ID: <255224dc-0a55-4a0c-95f3-b84d4c6b3897@redhat.com> Date: Mon, 13 Apr 2026 11:30:53 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] net: caif: fix stack out-of-bounds write in cfctrl_link_setup() To: Simon Horman , Kangzheng Gu Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, kees@kernel.org, thorsten.blum@linux.dev, arnd@arndb.de, sjur.brandeland@stericsson.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <0f9e9d4e-8083-4297-91d3-10d0f614c87c@redhat.com> <20260408125333.38489-1-xiaoguai0992@gmail.com> <20260412135743.GK469338@kernel.org> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260412135743.GK469338@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/12/26 3:57 PM, Simon Horman wrote: > I am wondering if it would be best to follow the pattern for > writing linkparam.u.utility.name elsewhere in this function. > That: > 1. Uses a somewhat more succinct loop control structure > 2. Silently truncates input without updating cmdrsp if overrun would occur > > Something like this (compile tested only!): > > diff --git a/net/caif/cfctrl.c b/net/caif/cfctrl.c > index c6cc2bfed65d..ba184c11386e 100644 > --- a/net/caif/cfctrl.c > +++ b/net/caif/cfctrl.c > @@ -15,6 +15,7 @@ > #include > > #define container_obj(layr) container_of(layr, struct cfctrl, serv.layer) > +#define RFM_VOLUME_LEN 20 > #define UTILITY_NAME_LENGTH 16 > #define CFPKT_CTRL_PKT_LEN 20 > > @@ -414,10 +415,11 @@ static int cfctrl_link_setup(struct cfctrl *cfctrl, struct cfpkt *pkt, u8 cmdrsp > */ > linkparam.u.rfm.connid = cfpkt_extr_head_u32(pkt); > cp = (u8 *) linkparam.u.rfm.volume; > - for (tmp = cfpkt_extr_head_u8(pkt); > - cfpkt_more(pkt) && tmp != '\0'; > - tmp = cfpkt_extr_head_u8(pkt)) > + caif_assert(sizeof(linkparam.u.rfm.volume) >= RFM_VOLUME_LEN); > + for(i = 0; i < RFM_VOLUME_LEN - 1 && cfpkt_more(pkt); i++) { > + tmp = cfpkt_extr_head_u8(pkt); > *cp++ = tmp; > + } > *cp = '\0'; > > if (CFCTRL_ERR_BIT & cmdrsp) I agree that the code suggested by Simon is clearer. Note that AFAICS it lacks an additional `tmp!= '\0'` check to break the loop, but even with that added it should be preferable. Thanks, Paolo