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 3013F3CF97E; Tue, 16 Jun 2026 18:05:57 +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=1781633158; cv=none; b=qGKc+vNTO13vpoyDSfre1t4T/6/p7TmMrhYh1CyzZtXOK5h6YzX0h1CkS5J71WvnMubY0Y5SzOYTX7EmMLnxOunb9K6ZlZ6//WkAwoWB4ioHVB87E/yhaVpcABjbrIypwNlkS4IBcaXCORax+kj6gGU8YkaBPyDguj0ZqWutjiI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781633158; c=relaxed/simple; bh=AYfaWnXMhQ/0ibIJXRrnx95M7Aspya4yzsA6GYZYrRk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WQ9YhQQLdFYSreDQUEGeRS2VCUjsLiaZQUea67nrszw8UbsddrIDyKVYcrH40Sg2fp0o1XUwIBbhUn4eNVryOGRf6MGN4+Jd2g6z/X0od4a5Id6WYJoAs1xN6E8i2nKSetFZRnOO2CYvDUv28hh5aZuhR24ag56IEcCHrSzgXLo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=a2JHjt+Q; 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="a2JHjt+Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 308291F000E9; Tue, 16 Jun 2026 18:05:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781633157; bh=wxpl7VJANQIBdWa/jfBRxcv0GFxUgyBK/2G4QIu1RvY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=a2JHjt+QfRh67WT0q8YVhL0kgzYOYOpUYkDUfJkzaUnPEL1L3pbUQqn6IColLh6iL KmmnaVk/xGpdkVtlFkJLZG8SoQQBAoVmzoZnY1Ld4zl4PMdZW3NPIeiTX8Lxoejsxv z4ZtFSrY+Fb0Tg2KqvXhRJVGPH2ZV0mTz/dl5A0A= 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 5.15 029/411] ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress() Date: Tue, 16 Jun 2026 20:24:27 +0530 Message-ID: <20260616145101.897086418@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145100.376842714@linuxfoundation.org> References: <20260616145100.376842714@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 5.15-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 343b957e6337ab..a25dfa59ca2196 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -557,7 +557,7 @@ 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