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=1793702873; b=snz6CKm7GXOUpfEeKqiktZLSafwUl3E6KycSspDBgkdH9wY1TzogQCQIACidLq8dB5eT sOAalEByOrgtzZUWTuV8aM1Ts+t4FZaXhtn6PsvuxuCBDi0UuvVzwWmLM5fi5wv6KdpuH bODvEZHF7cE/1mxx5BSG3MD761qkcGnpXKtqo9mAJ4JP01wRYPpP4iDuCPK9E1aewSMFu Aqu4nq37VhN/ROVb3Sjv2rwfQ7gEac1DWIitnHH37TQgHxUqJ6S8ce8+az4305gTa95a9 BRGvCzQo4bGQu/efA3I6Du9C4sQi9lSL2SadEK4EJRCmHAZU2Bp39dpXoUFltMA3u6w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793702873; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=0kmiHJ3wDzLz/EFRW/NORvp9X7k+9cgg6KB/pvVJlwA=; b=WUPYV1KqG6NJq1EthPNYBi1jo+2SJctlNqLWHcgwGoY/YSxYHddqTR1d+I/w8lEZWn+s 6bwHZE9l9VnvZd5drPOXeXKNlhjuY0TYNw+EEn27cAFECyGivdYXTIPU8Il0lPf7fI9aL nTyirlvk3njbmUHvmbVUBu3LY9l4u9/NaxRxQI5bV0j4u1vu/BJpwwx9x4CWQ2ZLFay+6 aui9526+IvpEizTemrdiof3hCSHCOLo/8ausf2J1BWP/BzC04OPepJoBcfgQ/mM/XJCx4 lzYTnNSJv5hUcR78N7AOZ6l/dFYMQ85JLFL2usWGam1YlhBGTsDUn462M+2uVlGLTwQ== 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=ZEqGUDPt; 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 BBE3E60736EF for ; Tue, 3 Nov 2026 10:47:52 +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=ZEqGUDPt Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4490A1F00A1B; Tue, 3 Nov 2026 10:47:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793702872; bh=0kmiHJ3wDzLz/EFRW/NORvp9X7k+9cgg6KB/pvVJlwA=; h=Subject:To:Cc:From:Date; b=ZEqGUDPt+OVMuCqari4XkeJVFSqvr3F7S9b7Yrb0wSPvcy8g8vb7FJwpURX3f32Hh cUJX2fml0u++NTvmer59AKxScQJKvo6hJcApMrTprKUWLhv+VbGtA/6ooYcN0oyOWJ uzEa9WjxLC+a9dAmsYXA01d5Z3BQ3O7AsqFV7M7Q= Subject: FAILED: patch "[PATCH] ksmbd: verify transform SessionId matches the decrypted" failed to apply to 6.18-stable tree To: zhangdairui@gmail.com,linkinjeon@kernel.org Cc: From: Date: Tue, 03 Nov 2026 11:46:43 +0100 Message-ID: <2026110343-kosher-bleach-17a4@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 798214e6fafcdcc29f5ba2661a473232b5e70cfb # git commit -s git send-email --to '' --in-reply-to '2026110343-kosher-bleach-17a4@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 798214e6fafcdcc29f5ba2661a473232b5e70cfb Mon Sep 17 00:00:00 2001 From: Dairui Zhang Date: Tue, 29 Sep 2026 22:30:00 +0800 Subject: [PATCH] ksmbd: verify transform SessionId matches the decrypted header 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 diff --git a/fs/smb/server/server.c b/fs/smb/server/server.c index 0827c8c51006..eb2952f2debe 100644 --- a/fs/smb/server/server.c +++ b/fs/smb/server/server.c @@ -187,6 +187,16 @@ static void __handle_ksmbd_work(struct ksmbd_work *work, 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 ksmbd_work *work, 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)) diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 45dce9c30b6b..0592e2539d1d 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -12256,6 +12256,60 @@ 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; diff --git a/fs/smb/server/smb2pdu.h b/fs/smb/server/smb2pdu.h index 40d61745ef41..c90a1d4e9f11 100644 --- a/fs/smb/server/smb2pdu.h +++ b/fs/smb/server/smb2pdu.h @@ -416,6 +416,7 @@ struct channel *lookup_chann_list(struct ksmbd_session *sess, 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);