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=1793827033; b=tI7g5655Limd75yIIcHMF4orFcp42lM6OT/sXjs+xj6KpyDkDgcb8jwy59KEoRIeFMhN W4MFX6BdE5DcOBrzWJYQvIrI4eGl8Db+x63R+tOei9h5WZXJXJ9NUlYemUsugZhotb2py Oi89SJz8I6Jj3v0tkZ2cDyZtKhHgTQ9yr61AFDYZt8ryxfyW7CFk4CK39WKRWxdEeopo6 0HUqLGEWWXqrP+sAWeuD9hocZJLlF0XfX/Jj6mmu348lx8J22DZVsW5Uv2wCxSrKfpj2E nErE1O3rjZQNzxzkBspPd/eajAVWqpYOZAluo/Fp77XeMpCK7plCe9lL/RdQKEmvMlg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793827033; 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=tcV0ajnol1GuX4HBGguuFlpB32F7zpYqf85sNQCqIow=; b=1rDcZPGPTfV80KRaTO5HxlFehWNNPOapaZ4jQ3FjAdEGpSebJulxSYVOWlj9GHklVvFh 2wdwguIEu/xAUGp8cG0RmqeGJEI3QBQTL4ChB5iw5g4bZ1F3X/swpB+Qleqj+uHrDQQkz CW7oBHIk7+eJ6FskSSVDZ7r3A0poS3Psq3tzkaIebkriCUP/OcFo40KoGh6GqpjENhxU1 DpTBnLazXdLhZ/VYd3Mm0YwPfG5ZAnvWMjRWL2ZuDD7tMr8OqSJ2wTzyVhL8KLEzDxh0e Rl/Ju53J4LeWhb23lr/j3gbNm+527yJkR3I8Im46AI5l4AQpyJuZiVy9H8wmQ7TZx8g== 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=l3Dr2JhX; 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 0CAF66070313; Wed, 4 Nov 2026 21:17:12 +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=l3Dr2JhX Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FD6F1F000C1; Wed, 4 Nov 2026 21:17:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793827032; bh=tcV0ajnol1GuX4HBGguuFlpB32F7zpYqf85sNQCqIow=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=l3Dr2JhX+3i/V8pyoMoJ1V6q50/tLW8CLoX3jZbtSiLTNYAeySd9q7SjPsSkIDLH1 BojRmQSxPaKMnbhYWSPyhdkW6Ni+DZau5hZcytipc2pciaPzpazWntr0U4/3cx0e7r u83iGdSJxtJVQsGpCLQEDW8lhL5VItCQHdSTK9fA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dairui Zhang , Namjae Jeon Subject: [PATCH 7.3 137/547] ksmbd: verify transform SessionId matches the decrypted header Date: Wed, 4 Nov 2026 16:05:21 -0500 Message-ID: <20261104211042.068358514@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211038.406938024@linuxfoundation.org> References: <20261104211038.406938024@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 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dairui Zhang commit 798214e6fafcdcc29f5ba2661a473232b5e70cfb upstream. When an encrypted request comes in, the decryption key is picked by the SessionId in the transform header, but the request is then authorized under whatever session the decrypted inner header names. Nothing ever compares the two, so on a connection with more than one session a client can get a request decrypted with one session's key and run it as another session. Encrypted requests are exempt from signing too, so a valid AEAD tag is the only proof of session identity, and it is checked against the wrong session. MS-SMB2 says the server must check that the transform SessionId matches the one in the decrypted SMB2 header and treat a mismatch as a protocol error. Add that check in __handle_ksmbd_work() after decryption, before dispatching: the message has to be at least one fixed SMB2 header, the first operation must not set SMB2_FLAGS_RELATED_OPERATIONS and its SessionId must match the transform SessionId, and every following non-related operation in a compound chain must carry the same SessionId. NextCommand offsets must be 8-byte aligned and stay inside the message; the bounds check is done by subtraction so it cannot wrap. When the decrypted payload is a compression transform, the existing decompression step runs first and the decompressed SMB2 message is checked instead, since a compression transform header carries no SessionId. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Reported-by: Dairui Zhang Assisted-by: LLM Cc: stable@vger.kernel.org Signed-off-by: Dairui Zhang Signed-off-by: Namjae Jeon Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/server.c | 16 ++++++++++++++ fs/smb/server/smb2pdu.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++ fs/smb/server/smb2pdu.h | 1 3 files changed, 71 insertions(+) --- a/fs/smb/server/server.c +++ b/fs/smb/server/server.c @@ -187,6 +187,16 @@ static void __handle_ksmbd_work(struct k if (conn->ops->is_transform_hdr && conn->ops->is_transform_hdr(work->request_buf)) { + u64 tr_sess_id; + + if (get_rfc1002_len(work->request_buf) < + sizeof(struct smb2_transform_hdr)) { + ksmbd_conn_abort(conn); + return; + } + tr_sess_id = le64_to_cpu(((struct smb2_transform_hdr *) + smb_get_msg(work->request_buf))->SessionId); + rc = conn->ops->decrypt_req(work); if (rc < 0) { ksmbd_conn_abort(conn); @@ -215,6 +225,12 @@ static void __handle_ksmbd_work(struct k ksmbd_conn_abort(conn); return; } + + rc = ksmbd_check_transform_session(work, tr_sess_id); + if (rc < 0) { + ksmbd_conn_abort(conn); + return; + } } if (conn->ops->allocate_rsp_buf(work)) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -12483,6 +12483,60 @@ bool smb3_is_transform_hdr(void *buf) return trhdr->ProtocolId == SMB2_TRANSFORM_PROTO_NUM; } +/* + * The decryption key is selected by the transform SessionId, but + * the request is authorized under the session named in the + * decrypted SMB2 header. Per MS-SMB2 the two must match, so check + * the decrypted message and its compound chain before dispatch. + */ +int ksmbd_check_transform_session(struct ksmbd_work *work, u64 tr_sess_id) +{ + struct smb2_hdr *hdr = smb_get_msg(work->request_buf); + size_t msg_len = get_rfc1002_len(work->request_buf); + size_t off = 0; + bool first = true; + + if (msg_len < sizeof(*hdr)) { + pr_err_ratelimited("Decrypted message is smaller than SMB2 header\n"); + return -ECONNABORTED; + } + + for (;;) { + u64 sid = le64_to_cpu(hdr->SessionId); + u32 next; + + if (first) { + if (hdr->Flags & SMB2_FLAGS_RELATED_OPERATIONS) { + pr_err_ratelimited("RELATED_OPERATIONS set on first operation\n"); + return -ECONNABORTED; + } + if (sid != tr_sess_id) { + pr_err_ratelimited("SessionId mismatch between transform and inner header\n"); + return -ECONNABORTED; + } + first = false; + } else if (!(hdr->Flags & SMB2_FLAGS_RELATED_OPERATIONS) && + sid != tr_sess_id) { + pr_err_ratelimited("SessionId mismatch in compound chain\n"); + return -ECONNABORTED; + } + + next = le32_to_cpu(hdr->NextCommand); + if (!next) + return 0; + if (next % 8) { + pr_err_ratelimited("NextCommand %u is not 8-byte aligned\n", next); + return -ECONNABORTED; + } + if (next > msg_len - off - sizeof(*hdr)) { + pr_err_ratelimited("NextCommand %u is out of the message\n", next); + return -ECONNABORTED; + } + off += next; + hdr = (struct smb2_hdr *)((u8 *)smb_get_msg(work->request_buf) + off); + } +} + int smb3_decrypt_req(struct ksmbd_work *work) { char *buf = work->request_buf; --- a/fs/smb/server/smb2pdu.h +++ b/fs/smb/server/smb2pdu.h @@ -420,6 +420,7 @@ struct channel *lookup_chann_list(struct void smb3_preauth_hash_rsp(struct ksmbd_work *work); bool smb3_is_transform_hdr(void *buf); int smb3_decrypt_req(struct ksmbd_work *work); +int ksmbd_check_transform_session(struct ksmbd_work *work, u64 tr_sess_id); int smb3_encrypt_resp(struct ksmbd_work *work); bool smb3_11_final_sess_setup_resp(struct ksmbd_work *work); int smb2_set_rsp_credits(struct ksmbd_work *work);