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 BC2B7534443; Thu, 17 Sep 2026 15:28:09 +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=1789658896; cv=none; b=Xb0ZJ3oNSlgRwJvNPs8/tXdi9pT26MES9MnWKEtzsr4WUClSxFv32vkrb3rP43ky+wm3FZX9rYhlrnHiueIpRyR8+qq3JXmCYV9AnNDBwBXn+CjY5bl8IRg6RmCJ2QEit2XltuWhJHFNqNcesO2IYVu3IuMNV0WSlrkDzglQwyQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789658896; c=relaxed/simple; bh=Ikh3o+mycYZO0+6DT36tSdgF9MQ8PC4GJkFjniDtFJM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rMr1ZDS4TBvo7u63+/hxiYfjGLZzuToAk6lylhcrBVCMSJ2HxxeSHszw4BsrXfHu4qz5Pa9Jjh3BbL9gRX1m/5yCn2BF/01AAkjxJkgdRtvLA1gRQf49SzYCa05ereztt7Jy2Xr9CphkgEiyhrcAmgvUE0iTr8ozpFZTNx8TOIA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=GZWi6OD0; 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="GZWi6OD0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E69E21F000FF; Thu, 17 Sep 2026 15:28:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789658889; bh=WQzX6YOKGJtJBTLVCaZ4mPXxw8Cmd2TgdBorR14U8TQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=GZWi6OD0fUXjPIWcqE/U46xdAOTiqq0zmWsDanJgH3e3M5KL00iR+NWIu7MPSOeCw QFf53EgKN00U5mYLNLCj5D/fvubJ9pfn38+OvaRwk/NBbRw9SWiK0kG4qGmjoza4vq Oh3zNtji5gYoOpqY8e9K0j+5sDk5FvvYmxnLsyHU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Henry Martin , Xin Long , Jakub Kicinski , Sasha Levin Subject: [PATCH 7.2 072/733] sctp: fix soft lockup from unpadded ASCONF-ACK parameter iteration Date: Thu, 17 Sep 2026 16:06:20 +0100 Message-ID: <20260917151352.660209310@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@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 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Henry Martin [ Upstream commit 2cb0b0b1ed69430bf73740377ea0a1c44c50db63 ] sctp_verify_asconf() walks ASCONF-ACK parameters with sctp_walk_params(), which advances by SCTP_PAD4(length), while the consumer sctp_get_asconf_response() iterates the same parameters advancing by the raw length, without padding. A single odd-length parameter desynchronises the two walks and makes the consumer interpret attacker-controlled bytes at a misaligned offset. When those bytes yield a length of zero, the while loop over asconf_ack_len makes no progress, spinning forever in softirq context, and the watchdog reports a soft lockup. All reads stay within the received skb, so the lockup is a pure remote denial of service. A remote peer can trigger it with a crafted ASCONF-ACK on an ADD-IP enabled association with an outstanding ASCONF (RFC 5061 section 4.1.2 requires the chunk to be authenticated, but the predefined empty key id 0 allows the peer to compute the same association HMAC from publicly exchanged parameters, so the gate does not help). The SCTP_PARAM_ERR_CAUSE case of sctp_verify_asconf() also performs no length check, letting a parameter without a complete error header reach the consumer, which reads errhdr.cause past the end of the parameter, an out-of-bounds read. Reject SCTP_PARAM_ERR_CAUSE parameters shorter than sizeof(struct sctp_addip_param) + sizeof(struct sctp_errhdr) at the verifier, and advance the consumer iterator with the same padding rule as the verifier to keep the two walks in lockstep. The verifier change guarantees a complete error header in every ERR_CAUSE parameter the consumer can see, so the consumer's asconf_ack_len check is dropped and it returns err_param->cause directly. The consumer padding fix is still required because odd lengths remain valid for SCTP_PARAM_ERR_CAUSE per RFC 5061. The issue was found by ZeroHive, a vulnerability hunting agent at Tencent Yunding Lab. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Henry Martin Acked-by: Xin Long Link: https://patch.msgid.link/20260828042431.3873725-1-bsdhenrymartin@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sctp/sm_make_chunk.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c index 236e25abc7a42..84a4c97d0f755 100644 --- a/net/sctp/sm_make_chunk.c +++ b/net/sctp/sm_make_chunk.c @@ -3215,6 +3215,9 @@ bool sctp_verify_asconf(const struct sctp_association *asoc, *errp = param.p; switch (param.p->type) { case SCTP_PARAM_ERR_CAUSE: + if (length < sizeof(struct sctp_addip_param) + + sizeof(struct sctp_errhdr)) + return false; break; case SCTP_PARAM_IPV4_ADDRESS: if (length != sizeof(struct sctp_ipv4addr_param)) @@ -3448,20 +3451,15 @@ static __be16 sctp_get_asconf_response(struct sctp_chunk *asconf_ack, case SCTP_PARAM_ERR_CAUSE: length = sizeof(*asconf_ack_param); err_param = (void *)asconf_ack_param + length; - asconf_ack_len -= length; - if (asconf_ack_len > 0) - return err_param->cause; - else - return SCTP_ERROR_INV_PARAM; - break; + return err_param->cause; default: return SCTP_ERROR_INV_PARAM; } } length = ntohs(asconf_ack_param->param_hdr.length); - asconf_ack_param = (void *)asconf_ack_param + length; - asconf_ack_len -= length; + asconf_ack_param = (void *)asconf_ack_param + SCTP_PAD4(length); + asconf_ack_len -= SCTP_PAD4(length); } return err_code; -- 2.53.0