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 326753438A6; Wed, 30 Sep 2026 18:01:18 +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=1790791279; cv=none; b=cbI9+Q3+k9NmJjHEXyWa+jIflxZenyiUgiC2gWIcF2TWsfZVB/6VL9SMxqDkrhXDE/TKOCspCCVq8UNTWEeVk75/7WF8X1M3WjPA1wwsFnXLuPQLjEcDViYoG5qJGEZyDbSEWDcTbL96SXl+4yBELR5/TCqOyfqswy80TcGwo7M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790791279; c=relaxed/simple; bh=QIvtaHXAAbXWdGmvBRnp6flDTbCemoVK5SCrgmTDVGM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=k2ga6iQiCEVjrfC2Fq0dDn5nUfs4TUCphUhqe8C+wU64GtB7T0H7kygRiGn3QWJIMyeYZNmRNcVAU8eVyWzdAHmCJMDgt/adxmXrQp0kuKqBKACn0rmwicfHJI3iiwpk31mimUySSH/ZELI6OipOuArZf9eoOe5xBk88DlLTFdI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WStk2hh5; 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="WStk2hh5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D3F21F000FF; Wed, 30 Sep 2026 18:01:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790791278; bh=J9IILYrPXZ1W3TqmFuy54Z9BwyY6K+ITpgWfNqvdKPg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WStk2hh5qUxxzedGmbmlnABtNsN0AoN2bV1MPwyDUG7oNdaLZFNpFFJTvZ+e6cQ9m UjcgReoqeHzhkyQKHmrjRwsMW4ZG3byftWCcxsX7OpHMSKiL/7KRhRBzoGoqu/k/AV Bd5cwOxvrRa7ARNFYZQrPnlfDO7NEsOFFCZC6lZc= 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 5.15 246/752] sctp: fix soft lockup from unpadded ASCONF-ACK parameter iteration Date: Wed, 30 Sep 2026 17:21:56 +0200 Message-ID: <20260930152403.596354451@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152358.131179731@linuxfoundation.org> References: <20260930152358.131179731@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: 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 6d738f95aff1d..649384ff0e547 100644 --- a/net/sctp/sm_make_chunk.c +++ b/net/sctp/sm_make_chunk.c @@ -3238,6 +3238,9 @@ 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)) @@ -3471,20 +3474,15 @@ 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