From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Thu, 02 Apr 2026 09:00:33 +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 1w8C2b-007lDe-0k for lore@lore.pengutronix.de; Thu, 02 Apr 2026 09:00:33 +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 1w8C2a-00042X-Lx for lore@pengutronix.de; Thu, 02 Apr 2026 09:00:33 +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=uWiCdjlaWpJFsrk5Syy9OK6gIFsMW82TY/H28GM3OvE=; b=Z5ZyAxWVcyYZdDh9oxNyG2n7E1 qaXwgihhu+ZSGVK0kI2hIY9OOj18Y0G7A7CZ2iYTczbLpDyXAbp5QIg0cUjPQs5bn1IbseSx+E+pA b3rZBw0CMe+RsC24DL0WnKE4heVNomj9CjbBPVBXmmjjmkF9e/jX2SoN64ljDEiHHgeEsKIiSKNw7 YrpRN7baMqQIiPIyf7sN93KrPokC8o4GxkdWDe5+TsWGadxm3l1z6wZaesdf0y8vXm9X1+nTJcDFv OFdb2EPLhlMZbct7JkDYXyiyCM66+vi+lZvYzbVW1w2LMDXwfi0jYY/j5nQmz+eLqY3UFACOYkO4l QSVFZwxg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w8C2E-0000000Gy7P-0NTx; Thu, 02 Apr 2026 07:00:10 +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 1w8C2C-0000000Gy5S-0low for barebox@lists.infradead.org; Thu, 02 Apr 2026 07:00:09 +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 1w8C22-0003ol-Oe; Thu, 02 Apr 2026 08:59:58 +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 1w8C22-003Kef-1o; Thu, 02 Apr 2026 08:59:58 +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 1w8C22-00000003O7L-21vN; Thu, 02 Apr 2026 08:59:58 +0200 From: Sascha Hauer Date: Thu, 02 Apr 2026 08:59:59 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260402-net-dhcp-buffer-overflows-v2-3-fe4ca7c4b718@pengutronix.de> References: <20260402-net-dhcp-buffer-overflows-v2-0-fe4ca7c4b718@pengutronix.de> In-Reply-To: <20260402-net-dhcp-buffer-overflows-v2-0-fe4ca7c4b718@pengutronix.de> To: BAREBOX X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1775113198; l=1084; i=s.hauer@pengutronix.de; s=20230412; h=from:subject:message-id; bh=WT5PP4JpEeGOb81uDXm3uKSzyGFCMl73mwjL8xMWlWc=; b=7NwP38UxzYoU2VWw9pK+9CEkj2XiykJfnk5G1+5FFmckCCQo6wMINSw/TLMvPFEiOOXHzfx5M jrl/N+FyKKRBuStz6p1pVCisD5VrOkU7LGh4Fe6FegMjEmwGo8TrwmP 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-20260402_000008_241913_BD0178CF X-CRM114-Status: GOOD ( 10.75 ) 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 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) 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 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); -- 2.47.3