From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Thu, 02 Apr 2026 08:57:03 +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 1w8BzD-007l8x-0x for lore@lore.pengutronix.de; Thu, 02 Apr 2026 08:57:03 +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 1w8BzC-000321-He for lore@pengutronix.de; Thu, 02 Apr 2026 08:57:03 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:To:In-Reply-To: References:Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version: Subject:Date:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=acG9u7mMRCkc14HEV/15AnZL2KPGJ8KcIUlwtH1S5M4=; b=YxjK9nHGRp3evNwDAT46VeG5Hk 4SqmMISel7R2VEwFvlDywpW9SzeQ7PxoYlsxun1JrOcECjnJUFaKt2bw9LhaatSFS+Tbp1NuxPjXf OVxW3aHUUQChVmHsSUGqVVNeQ4nlcNXUAgbtqp4eCFnxrZXi6UPzRxuSd60UIX3slmoR+9A4ps6kH Sw5KLKb98fJXqiF8KjIT51cpMPpquOHIKnCwreaXpN6fcYaqUkSNMOa7G+rF3EtN7B2p5RASgyVda HodZPLC9yhUks1eT5XIdTGEwKAd8Y848DhkICAwIPZPyzOw3s74Wjn7V//q1ri9mvBxVJygajmSSn wvQ78LTg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w8Byl-0000000GxHE-25Lo; Thu, 02 Apr 2026 06:56:35 +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 1w8Byi-0000000GxFf-0hqs for barebox@lists.infradead.org; Thu, 02 Apr 2026 06:56:33 +0000 Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1w8Byg-0002oH-HX; Thu, 02 Apr 2026 08:56:30 +0200 Received: from dude02.red.stw.pengutronix.de ([2a0a:edc0:0:1101:1d::28]) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1w8Byg-003KeE-0w; Thu, 02 Apr 2026 08:56:30 +0200 Received: from [::1] (helo=dude02.red.stw.pengutronix.de) by dude02.red.stw.pengutronix.de with esmtp (Exim 4.98.2) (envelope-from ) id 1w8Byg-00000003Nta-0tEo; Thu, 02 Apr 2026 08:56:30 +0200 From: Sascha Hauer Date: Thu, 02 Apr 2026 08:56:31 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260402-net-dhcp-buffer-overflows-v1-3-cd60b651a629@pengutronix.de> References: <20260402-net-dhcp-buffer-overflows-v1-0-cd60b651a629@pengutronix.de> In-Reply-To: <20260402-net-dhcp-buffer-overflows-v1-0-cd60b651a629@pengutronix.de> To: BAREBOX X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1775112990; l=1084; i=s.hauer@pengutronix.de; s=20230412; h=from:subject:message-id; bh=DJpb6z2U7NGGbSKS3QGYExbzvkDTktAGjLrvsipYN2A=; b=zLgUQrlotwnsYK6QeMHB77lGw8JVKktTNp7aNHAluItOhthcJ4D9ZQQIynK1KCodaX8yYVhFd YpWbOWbgFBXBrOP5mmn01Mk/0xomfx6D10cGj3iaz2AJ8tidKRRSpEE X-Developer-Key: i=s.hauer@pengutronix.de; a=ed25519; pk=4kuc9ocmECiBJKWxYgqyhtZOHj5AWi7+d0n/UjhkwTg= X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260401_235632_237028_BBB8E471 X-CRM114-Status: GOOD ( 10.45 ) 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: , Cc: "Claude Opus 4.6 \(1M context\)" 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=unavailable autolearn_force=no version=3.4.2 Subject: [PATCH 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) 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) --- net/dhcp.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/dhcp.c b/net/dhcp.c index c77dcc41d8..112b68ef4c 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); -- 2.47.3