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=1793720847; b=IJEPEevg2uXOf2695GUGENlJMKBWtsRHwXdT2Sz//6WncQLTBq4jVTNE0rGDS0Q82oTB cxUwdjZDPfc6PNAtsIBduY7a1uXyhgZGv8mXVexQSCtP9wSMWZdZbgO1SQamD+lxCKCoX osj0C2GJH4LLMAr96Ym6rQt6KjCrGpHGCHt23bCnZLKbMveX3nSu0tUHClXHuvVoa4opJ gNz0rHsv9YnwuZA/J5oDSQH6CxeIQknccxqEsYjbeAxeVo/HJQgUlaoecz58X3bRSt6HQ nSl94FsIm1fFB37CHBTE/alJKhMX2JcCsbntpd9wtiHQCBfHEQRYxw1PVHEFoNooOiQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793720847; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=dKPJ6608J1BqVOjmF+cq8HEpkC2n601wwA1rhFj66w4=; b=KCDmGWGgnbXDM+m6AcDQseDF9zG+GxpAfGRIPmISuQakWSyYyn7sqRf1fa+l9UNNcK1c Ky4mmSH1WOVgTc/4AIMuGJokG18Zhkxzx8VSXql4D3+vBMuPakDSGrRQ3rUeNvZjKSSII i9kuJyyhXTEU5ygqqNgUN6NH4FfFZ9OXW9Ilpg66pEXRKcPT1GXBrrOif+kPtyN/Fe699 dTSj4TfTvJcTjZZW5mj1osW0lzHfqlM25jCQgueplHrS28+9BTDQOIEnYhsRZl1xjfPMd GRitC0J6eRxK5M9+2S/kF9QiEySAzuydcLvm3aqBpUVpt9sbQ+hSxPeB+ptXxzXBmYQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=MXHdRPS1; 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 226AD606A326 for ; Tue, 3 Nov 2026 15:47:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=MXHdRPS1 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D2DF1F000C1; Tue, 3 Nov 2026 15:47:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793720846; bh=dKPJ6608J1BqVOjmF+cq8HEpkC2n601wwA1rhFj66w4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=MXHdRPS18lxq/byU2fXVBp/jBLu9p7quEUeICn3IdmOohgubG8JHgkS6q+Ntg5AcV FJ6BtSskaGKZlXFxuEOHymvYvW4WFf4nwagnK14N1gk9GK68UpE9VVXUCczXb36fbZ UQpGsa/N9qUtWORs7k2csTAf6l7JeXDM7PQAIjA1ql4hZ6YRvWVsW3eTG1vZ63FyFN 166dvLg6kGLXylBcBYA/N7W1ZOhSm7+ifwT89OM9aBlLvp1UDuDokEsp+5NIz3S33Z ihU6oS9zk0euea/ycvGqeNl/TVRPrdjh27hHKB+w54FdykhnJf2uerFJvILDm8vGAB vE6Gyh5UgoHcA== From: Sasha Levin To: stable@vger.kernel.org Cc: Namjae Jeon , zdi-disclosures@trendmicro.com, Sasha Levin Subject: [PATCH 6.18.y] ksmbd: prevent stale data from being written by SMB2 WRITE requests Date: Tue, 3 Nov 2026 10:47:24 -0500 Message-ID: <20261103154703.377857-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110350-lustfully-linoleum-666e@gregkh> References: <2026110350-lustfully-linoleum-666e@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-Transfer-Encoding: 8bit From: Namjae Jeon [ Upstream commit bc0e0f5ac1d7b044d403f859406b4b66d4b1ce9b ] Initialize the compatibility byte in request buffers without zeroing the entire allocation. Keep the one-byte compatibility exception for SMB2 messages so valid zero-length WRITE requests remain compatible, and validate the data range in the WRITE handlers against the current compound request before accessing it. This prevents stale request-buffer data from being written to files or sent to IPC pipes. Fixes: 443d61d1fa9f ("ksmbd: allocate one more byte for implied bcc[0]") Cc: stable@vger.kernel.org Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-32436 Signed-off-by: Namjae Jeon [ sashal: Inlined the unavailable smb2_current_req_len() helper and omitted the decompression change because compression support is absent. ] Signed-off-by: Sasha Levin --- fs/smb/server/connection.c | 1 + fs/smb/server/smb2pdu.c | 34 +++++++++++++++++++++++++--------- 2 files changed, 26 insertions(+), 9 deletions(-) diff --git a/fs/smb/server/connection.c b/fs/smb/server/connection.c index 8f1b70e39362e..e8739b482b2fe 100644 --- a/fs/smb/server/connection.c +++ b/fs/smb/server/connection.c @@ -520,6 +520,7 @@ int ksmbd_conn_handler_loop(void *p) if (!conn->request_buf) break; + conn->request_buf[pdu_size + 4] = 0; memcpy(conn->request_buf, hdr_buf, sizeof(hdr_buf)); /* diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 793c219b9a610..22eb73bb66c44 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -7202,23 +7202,28 @@ static noinline int smb2_write_pipe(struct ksmbd_work *work) int err = 0, ret = 0; char *data_buf; size_t length; + unsigned int data_offset, req_len; WORK_BUFFERS(work, req, rsp); length = le32_to_cpu(req->Length); id = req->VolatileFileId; + data_offset = le16_to_cpu(req->DataOffset); + req_len = le32_to_cpu(req->hdr.NextCommand); + if (!req_len) + req_len = get_rfc1002_len(work->request_buf) - + work->next_smb2_rcv_hdr_off; - if ((u64)le16_to_cpu(req->DataOffset) + length > - get_rfc1002_len(work->request_buf)) { - pr_err("invalid write data offset %u, smb_len %u\n", - le16_to_cpu(req->DataOffset), - get_rfc1002_len(work->request_buf)); + if (data_offset < offsetof(struct smb2_write_req, Buffer) || + data_offset > req_len || length > req_len - data_offset) { + pr_err("invalid write data offset %u, length %zu, req_len %u\n", + data_offset, length, req_len); err = -EINVAL; goto out; } data_buf = (char *)(((char *)&req->hdr.ProtocolId) + - le16_to_cpu(req->DataOffset)); + data_offset); rpc_resp = ksmbd_rpc_write(work->sess, id, data_buf, length); if (rpc_resp) { @@ -7375,14 +7380,25 @@ int smb2_write(struct ksmbd_work *work) writethrough = true; if (is_rdma_channel == false) { - if (le16_to_cpu(req->DataOffset) < - offsetof(struct smb2_write_req, Buffer)) { + unsigned int data_offset = le16_to_cpu(req->DataOffset); + unsigned int req_len = le32_to_cpu(req->hdr.NextCommand); + + if (!req_len) + req_len = get_rfc1002_len(work->request_buf) - + work->next_smb2_rcv_hdr_off; + + if (data_offset < offsetof(struct smb2_write_req, Buffer) || + data_offset > req_len || + length > req_len - data_offset) { + ksmbd_debug(SMB, + "invalid write data offset %u, length %zu, req_len %u\n", + data_offset, length, req_len); err = -EINVAL; goto out; } data_buf = (char *)(((char *)&req->hdr.ProtocolId) + - le16_to_cpu(req->DataOffset)); + data_offset); ksmbd_debug(SMB, "filename %pD, offset %lld, len %zu\n", fp->filp, offset, length); -- 2.53.0