From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Fri, 17 Apr 2026 11:50:25 +0200 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1wDfqD-00D9C9-1a for lore@lore.pengutronix.de; Fri, 17 Apr 2026 11:50:25 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1wDfqC-0007oG-U2 for lore@pengutronix.de; Fri, 17 Apr 2026 11:50:25 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=AVUG65yZ+aCWvKJ6kD1G7uOUJWBRav4T0T2Dz6DQ2Q4=; b=vd/iBT4nzbuhh1h3ydYxUjNgp2 CPcwdE4+sR/NQZByaBTXqrdyHwDq+lXGBQHgny0AmNzZRz/UJBBKhjKuSTvk2GXOint6tWGlwwy0L 1Zun1GaE+tnzHjA7LjDbcruA5hjd5TWa6d6wAUFRK4O8K9+rwbhEAMLHx197f8uQl6/Y4YS7P0Nfs ujpJCOGss8UPca+eBkQxdd9a/NUJidJA3qIsI7HVdVlO4ps0hTXnckBqOgeue9JCbVjjh535ILBT8 bsUUDl83sQH1sTCJKF1VstEr39Ixta0E+8Y8cocj7HpWXrnP1/gPzP5dJsHJN6V/sCAPjsmFJBU1Q 0Vr08PPA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDfpn-00000003rLE-0w0A; Fri, 17 Apr 2026 09:49:59 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDfpk-00000003rK6-2Cr1 for barebox@lists.infradead.org; Fri, 17 Apr 2026 09:49:58 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1wDfpi-0007df-UZ; Fri, 17 Apr 2026 11:49:54 +0200 Message-ID: <9ab4089e-f8ae-45e0-96d0-0bba9d7cb4b8@pengutronix.de> Date: Fri, 17 Apr 2026 11:49:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Sascha Hauer , BAREBOX Cc: "Claude Opus 4.6 (1M context)" References: <20260402-net-dhcp-buffer-overflows-v2-0-fe4ca7c4b718@pengutronix.de> <20260402-net-dhcp-buffer-overflows-v2-3-fe4ca7c4b718@pengutronix.de> Content-Language: en-US, de-DE, de-BE From: Ahmad Fatoum In-Reply-To: <20260402-net-dhcp-buffer-overflows-v2-3-fe4ca7c4b718@pengutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260417_024956_567090_13FA8D98 X-CRM114-Status: GOOD ( 18.16 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-5.2 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.2 Subject: Re: [PATCH v2 3/3] net: dhcp: cap DHCP option string length to 255 bytes X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) On 4/2/26 8:59 AM, Sascha Hauer wrote: > dhcp_set_string_options() stores the string length in a u8 field but > uses the full strlen() value for memcpy(). If a user sets a DHCP > option string (hostname, vendor_id, etc.) longer than 255 bytes, the > length field silently truncates while memcpy() copies the full string, > writing past the expected region in the packet buffer. > > Cap str_len at 255 to match the maximum DHCP option length defined by > RFC2132, ensuring the length field and memcpy are consistent. > > Signed-off-by: Sascha Hauer > Co-Authored-By: Claude Opus 4.6 (1M context) Reviewed-by: Ahmad Fatoum > --- > net/dhcp.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/dhcp.c b/net/dhcp.c > index f4e4033351..21d48cfcf2 100644 > --- a/net/dhcp.c > +++ b/net/dhcp.c > @@ -173,6 +173,10 @@ static int dhcp_set_string_options(int option, const char *str, u8 *e) > if (!str_len) > return 0; > > + /* DHCP option length field is a single byte per RFC2132 */ > + if (str_len > 255) > + str_len = 255; > + > *e++ = option; > *e++ = str_len; > memcpy(e, str, str_len); > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |