From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AE6A74071DA; Sun, 7 Jun 2026 10:20:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780827607; cv=none; b=mR3CTqF1pD+2VJXH6LSxXbzX90NSfMMCb6T4NROgyOVVZkC5kz8xPdaSHvWA8LnN0TlQIArxxOyJVOkeBIo4tD1o0z9YOo3AFXtpk1ueXSXmPFQ+H/cYM4kIgkmKPYRCBtIQgdEfAhPG/2MUZT7/GW65QccTF6rT9ErJlERZ7tk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780827607; c=relaxed/simple; bh=aYJfX+oU82WX9sveeuBE+dTzZ8EuE7FEzuMTkDz3Oo4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eMpTFvR+VcNCOkdFy0Oa8f0Qgksodm0Z+b3AR+ZrLHnGnXUTcRLLpOuiRCP36VI7tpjuCsCXQt2+eb88FoVvgnL55fnXsIVeZjATzN9dZZpGVAiReAmMtAZzwps2Sht1xfXv4AyNOFt/lSxnsnAPupEFllOiV7llFbMT7dG8vyk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZtMZZPM4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ZtMZZPM4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EFDB71F00893; Sun, 7 Jun 2026 10:20:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780827606; bh=W0kJmFq2mfpbyeKzIfcsKaxyq8CWsQKRoGvvuLrMbe0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZtMZZPM4WWXZlsHDqtMTLnGWrvC3DNcYQaxLXtlvnV95Xb3pQuVMdm/9wJ2reqayY EwGsth528cYVnEEz7E86AcbKEQV72G6iilcgHbKGwZskYIWVf5VDVk3yNwWOvkCeBQ IsmGHpozD/622qvL08OA9bzna4DQCtL/+XFzERw8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Rahul Chandelkar , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.12 072/307] ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress() Date: Sun, 7 Jun 2026 11:57:49 +0200 Message-ID: <20260607095730.406974179@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260607095727.647295505@linuxfoundation.org> References: <20260607095727.647295505@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Rahul Chandelkar [ Upstream commit 9d5e7a46a9f6d8f503b41bfefef70659845f1679 ] ipv6_rpl_srh_decompress() computes: outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3); hdrlen is __u8. For n >= 127 the result exceeds 255 and silently truncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16): (128 * 16) >> 3 = 256, truncated to 0 as __u8 The caller in ipv6_rpl_srh_rcv() then places the compressed header at buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8, but the decompressed region occupies buf[0..2055] (8-byte header plus 128 full addresses). The compressed header overlaps the decompressed data, and ipv6_rpl_srh_compress() writes into this overlap, corrupting the routing header of the forwarded packet. The existing guard at exthdrs.c:546 checks (n + 1) > 255, which prevents n+1 from overflowing unsigned char (the segments_left field), but does not prevent the computed hdrlen from overflowing __u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not fit. Tighten the bound to (n + 1) > 127. This caps n at 126, giving hdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed header then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly past the decompressed region (buf[0..2039]). No overlap. 127 segments is well beyond any realistic RPL deployment. Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr") Signed-off-by: Rahul Chandelkar Link: https://patch.msgid.link/20260525154031.2290876-1-rc@rexion.ai Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/exthdrs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c index 5ef6fbc66beb11..43e34fe448ffe5 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -546,7 +546,7 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb) * unsigned char which is segments_left field. Should not be * higher than that. */ - if (r || (n + 1) > 255) { + if (r || (n + 1) > 127) { kfree_skb(skb); return -1; } -- 2.53.0