From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793211960; b=I+uisYu+Hbft89Qr6TR67dGI+rGSd5BqLaRWo5OzoSEasqLHJvNT5j+DCrmPt+IVwT8F 69XHajGr6c8XQfvgU7GjqzOn4Z23V2oad/iAoPac4VKmC+Gf4wzLN1jSZEnzIQDoaF2kf N6b5JqdjnD6C1IqZ1BJEzUOzAGsWUqN7l7xw9g7ZWVKFCgz+INpWSNli+pr7mALIsTVSt k4B6Pjfpt9cpGpSIu+GtCmEnWWP6s/WAMwLFcu7ccLDANruiBkjkBJ6ZV9c6r76j7fIdt joauT+KHc2clid0bo8UHJ8WGZ3LxLSmxWScmKS01C2c6SlKixid9igcYR8U/GooXeqA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793211960; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=kZxIhZFOHNqbfukmd7aKlZxvDzTm4Xf8Wt1fefBAjvo=; b=vzSmuL3yj4uro1cgI5a8yz5K3ZGzw5J+sKhK63l2HZu5zX4z1v3ansvm6/RgjeWdr8Mu kqOF/ZYqtp+bxg5+7XGrlIwesqg5q03YZ6PQRk5E2U7hFm6fcVtRIeBvix8zNvvRTZhva 4bYakriXMJy4vB7NkgNK9NafYyaLLCAV7UxFKvV+eLa0Wu4h9442dT/O6jnzXrIoUgCUh 23T42vztIFhPulvMO07gvHfVrPELS5xUyMM/YQ3hWPIC7gs8Sjd/HfxOQrxwdVrV5PyFq r9R51Pe1QWNVk/ZU/dFYKeZnDRNhqElxMMSij6UElmFgX+XJokDBECt8FCVUT38Ovhw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=J8xJYwdC; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 747E5606A31C; Wed, 28 Oct 2026 18:26:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=J8xJYwdC Received: by smtp.kernel.org (Postfix) with ESMTPSA id C543D1F01825; Wed, 28 Oct 2026 18:25:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793211960; bh=kZxIhZFOHNqbfukmd7aKlZxvDzTm4Xf8Wt1fefBAjvo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=J8xJYwdC3vdSX6W52B7ZTP+eXUOUUF8y4TJWIP9QJkU7VOuKxhd6jCkwhyRHHJKGL LspAlhv5c4aU341sEzGbogGeIHQI338h2o3s+AoHSdfaey+oejtFCJ/aJgKUNw9gz7 osQ12yfIcadUwMNCom6ai5ZG8X4v1wkOUm81VzJI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Charles Vosburgh , Xin Long , Jakub Kicinski Subject: [PATCH 5.15 516/571] sctp: validate chunk length in the inqueue parser Date: Wed, 28 Oct 2026 18:01:03 +0100 Message-ID: <20261028170020.274043665@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170008.009143722@linuxfoundation.org> References: <20261028170008.009143722@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Charles Vosburgh commit 6cfc1b90cb86f4aabc69fb8e30128e07e2cdfa3a upstream. SCTP chunks always include a four-byte generic header, but sctp_inq_pop() currently accepts shorter declared lengths. A zero-length chunk leaves chunk_end at the current header. When ASCONF is covered by the association's SCTP-AUTH policy, sctp_assoc_bh_rcv() can continue before the state machine performs its normal chunk-length check. sctp_inq_pop() then returns the same malformed chunk repeatedly and the receive softirq can lock up. A remote SCTP peer can trigger this after establishing an association on a kernel built with CONFIG_IP_SCTP and configured with net.sctp.addip_enable=1 and net.sctp.auth_enable=1. The reproducer did not require application credentials, a shared SCTP AUTH key, or net.sctp.addip_noauth_enable=1. On commit f967455fb2a5 ("seg6: reset IP6CB after IPv6 decapsulation"), one zero-length ASCONF caused repeated watchdog soft-lockup reports in a two-vCPU KVM guest. All 3 pre-trigger health probes succeeded, while 36 of 37 post-trigger probes failed. With this change, all 37 post-trigger probes succeeded and no equivalent soft-lockup signature appeared. Reject chunks shorter than the generic SCTP header at the shared inqueue parser boundary. Mark the packet for discard before either caller can continue processing it, while preserving the four-byte generic minimum. Declared-length 1 through 4 controls and kernel-generated ASCONF traffic remained healthy. The patched sctp_hello selftest passed for IPv4 and IPv6. The complete private reproducer and validation evidence are available directly to maintainers on request. Fixes: bbd0d59809f9 ("[SCTP]: Implement the receive and verification of AUTH chunk") Cc: stable@vger.kernel.org Signed-off-by: Charles Vosburgh Acked-by: Xin Long Link: https://patch.msgid.link/20260827-sctp-zero-chunk-inqueue-v2-1-2e7669c6a6cb@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/sctp/inqueue.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/net/sctp/inqueue.c +++ b/net/sctp/inqueue.c @@ -206,8 +206,10 @@ new_skb: chunk->chunk_end = ((__u8 *)ch) + SCTP_PAD4(ntohs(ch->length)); skb_pull(chunk->skb, sizeof(*ch)); chunk->subh.v = NULL; /* Subheader is no longer valid. */ - - if (chunk->chunk_end + sizeof(*ch) <= skb_tail_pointer(chunk->skb)) { + if (unlikely(ntohs(ch->length) < sizeof(*ch))) { + chunk->pdiscard = 1; + } else if (chunk->chunk_end + sizeof(*ch) <= + skb_tail_pointer(chunk->skb)) { /* This is not a singleton */ chunk->singleton = 0; } else if (chunk->chunk_end > skb_tail_pointer(chunk->skb)) {