ksmbd: fix slab-out-of-bounds in init_smb2_rsp_hdr

When smb1 mount fails, KASAN detect slab-out-of-bounds in
init_smb2_rsp_hdr like the following one.
For smb1 negotiate(56bytes) , init_smb2_rsp_hdr() for smb2 is called.
The issue occurs while handling smb1 negotiate as smb2 server operations.
Add smb server operations for smb1 (get_cmd_val, init_rsp_hdr,
allocate_rsp_buf, check_user_session) to handle smb1 negotiate so that
smb2 server operation does not handle it.

[  411.400423] CIFS: VFS: Use of the less secure dialect vers=1.0 is
not recommended unless required for access to very old servers
[  411.400452] CIFS: Attempting to mount \\192.168.45.139\homes
[  411.479312] ksmbd: init_smb2_rsp_hdr : 492
[  411.479323] ==================================================================
[  411.479327] BUG: KASAN: slab-out-of-bounds in
init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd]
[  411.479369] Read of size 16 at addr ffff888488ed0734 by task kworker/14:1/199

[  411.479379] CPU: 14 PID: 199 Comm: kworker/14:1 Tainted: G
 OE      6.1.21 #3
[  411.479386] Hardware name: ASUSTeK COMPUTER INC. Z10PA-D8
Series/Z10PA-D8 Series, BIOS 3801 08/23/2019
[  411.479390] Workqueue: ksmbd-io handle_ksmbd_work [ksmbd]
[  411.479425] Call Trace:
[  411.479428]  <TASK>
[  411.479432]  dump_stack_lvl+0x49/0x63
[  411.479444]  print_report+0x171/0x4a8
[  411.479452]  ? kasan_complete_mode_report_info+0x3c/0x200
[  411.479463]  ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd]
[  411.479497]  kasan_report+0xb4/0x130
[  411.479503]  ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd]
[  411.479537]  kasan_check_range+0x149/0x1e0
[  411.479543]  memcpy+0x24/0x70
[  411.479550]  init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd]
[  411.479585]  handle_ksmbd_work+0x109/0x760 [ksmbd]
[  411.479616]  ? _raw_spin_unlock_irqrestore+0x50/0x50
[  411.479624]  ? smb3_encrypt_resp+0x340/0x340 [ksmbd]
[  411.479656]  process_one_work+0x49c/0x790
[  411.479667]  worker_thread+0x2b1/0x6e0
[  411.479674]  ? process_one_work+0x790/0x790
[  411.479680]  kthread+0x177/0x1b0
[  411.479686]  ? kthread_complete_and_exit+0x30/0x30
[  411.479692]  ret_from_fork+0x22/0x30
[  411.479702]  </TASK>

Fixes: 39b291b ("ksmbd: return unsupported error on smb1 mount")
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/server.c

@@ -289,10 +289,7 @@ static int queue_ksmbd_work(struct ksmbd_conn *conn)
 	work->request_buf = conn->request_buf;
 	conn->request_buf = NULL;
 
-	if (ksmbd_init_smb_server(work)) {
-		ksmbd_free_work_struct(work);
-		return -EINVAL;
-	}
+	ksmbd_init_smb_server(work);
 
 	ksmbd_conn_enqueue_request(work);
 	atomic_inc(&conn->r_count);

fs/ksmbd/smb2pdu.c

@@ -229,9 +229,6 @@ int init_smb2_neg_rsp(struct ksmbd_work *work)
 	struct smb2_negotiate_rsp *rsp;
 	struct ksmbd_conn *conn = work->conn;
 
-	if (conn->need_neg == false)
-		return -EINVAL;
-
 	*(__be32 *)work->response_buf =
 		cpu_to_be32(conn->vals->header_size);
 

fs/ksmbd/smb_common.c

@@ -283,20 +283,121 @@ static int ksmbd_negotiate_smb_dialect(void *buf)
 	return BAD_PROT_ID;
 }
 
-int ksmbd_init_smb_server(struct ksmbd_work *work)
+#define SMB_COM_NEGOTIATE_EX	0x0
+
+/**
+ * get_smb1_cmd_val() - get smb command value from smb header
+ * @work:	smb work containing smb header
+ *
+ * Return:      smb command value
+ */
+static u16 get_smb1_cmd_val(struct ksmbd_work *work)
 {
-	struct ksmbd_conn *conn = work->conn;
+	return SMB_COM_NEGOTIATE_EX;
+}
 
-	if (conn->need_neg == false)
+/**
+ * init_smb1_rsp_hdr() - initialize smb negotiate response header
+ * @work:	smb work containing smb request
+ *
+ * Return:      0 on success, otherwise -EINVAL
+ */
+static int init_smb1_rsp_hdr(struct ksmbd_work *work)
+{
+	struct smb_hdr *rsp_hdr = (struct smb_hdr *)work->response_buf;
+	struct smb_hdr *rcv_hdr = (struct smb_hdr *)work->request_buf;
+
+	/*
+	 * Remove 4 byte direct TCP header.
+	 */
+	*(__be32 *)work->response_buf =
+		cpu_to_be32(sizeof(struct smb_hdr) - 4);
+
+	rsp_hdr->Command = SMB_COM_NEGOTIATE;
+	*(__le32 *)rsp_hdr->Protocol = SMB1_PROTO_NUMBER;
+	rsp_hdr->Flags = SMBFLG_RESPONSE;
+	rsp_hdr->Flags2 = SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS |
+		SMBFLG2_EXT_SEC | SMBFLG2_IS_LONG_NAME;
+	rsp_hdr->Pid = rcv_hdr->Pid;
+	rsp_hdr->Mid = rcv_hdr->Mid;
+	return 0;
+}
+
+/**
+ * smb1_check_user_session() - check for valid session for a user
+ * @work:	smb work containing smb request buffer
+ *
+ * Return:      0 on success, otherwise error
+ */
+static int smb1_check_user_session(struct ksmbd_work *work)
+{
+	unsigned int cmd = work->conn->ops->get_cmd_val(work);
+
+	if (cmd == SMB_COM_NEGOTIATE_EX)
 		return 0;
 
-	init_smb3_11_server(conn);
+	return -EINVAL;
+}
+
+/**
+ * smb1_allocate_rsp_buf() - allocate response buffer for a command
+ * @work:	smb work containing smb request
+ *
+ * Return:      0 on success, otherwise -ENOMEM
+ */
+static int smb1_allocate_rsp_buf(struct ksmbd_work *work)
+{
+	work->response_buf = kmalloc(MAX_CIFS_SMALL_BUFFER_SIZE,
+			GFP_KERNEL | __GFP_ZERO);
+	work->response_sz = MAX_CIFS_SMALL_BUFFER_SIZE;
+
+	if (!work->response_buf) {
+		pr_err("Failed to allocate %u bytes buffer\n",
+				MAX_CIFS_SMALL_BUFFER_SIZE);
+		return -ENOMEM;
+	}
 
-	if (conn->ops->get_cmd_val(work) != SMB_COM_NEGOTIATE)
-		conn->need_neg = false;
 	return 0;
 }
 
+static struct smb_version_ops smb1_server_ops = {
+	.get_cmd_val = get_smb1_cmd_val,
+	.init_rsp_hdr = init_smb1_rsp_hdr,
+	.allocate_rsp_buf = smb1_allocate_rsp_buf,
+	.check_user_session = smb1_check_user_session,
+};
+
+static int smb1_negotiate(struct ksmbd_work *work)
+{
+	return ksmbd_smb_negotiate_common(work, SMB_COM_NEGOTIATE);
+}
+
+static struct smb_version_cmds smb1_server_cmds[1] = {
+	[SMB_COM_NEGOTIATE_EX]	= { .proc = smb1_negotiate, },
+};
+
+static void init_smb1_server(struct ksmbd_conn *conn)
+{
+	conn->ops = &smb1_server_ops;
+	conn->cmds = smb1_server_cmds;
+	conn->max_cmds = ARRAY_SIZE(smb1_server_cmds);
+}
+
+void ksmbd_init_smb_server(struct ksmbd_work *work)
+{
+	struct ksmbd_conn *conn = work->conn;
+	__le32 proto;
+
+	if (conn->need_neg == false)
+		return;
+
+	proto = *(__le32 *)((struct smb_hdr *)work->request_buf)->Protocol;
+	if (proto == SMB1_PROTO_NUMBER)
+		init_smb1_server(conn);
+	else
+		init_smb3_11_server(conn);
+}
+
 int ksmbd_populate_dot_dotdot_entries(struct ksmbd_work *work, int info_level,
 				      struct ksmbd_file *dir,
 				      struct ksmbd_dir_info *d_info,
@@ -444,20 +545,10 @@ static int smb_handle_negotiate(struct ksmbd_work *work)
 
 	ksmbd_debug(SMB, "Unsupported SMB1 protocol\n");
 
-	/*
-	 * Remove 4 byte direct TCP header, add 2 byte bcc and
-	 * 2 byte DialectIndex.
-	 */
-	*(__be32 *)work->response_buf =
-		cpu_to_be32(sizeof(struct smb_hdr) - 4 + 2 + 2);
+	/* Add 2 byte bcc and 2 byte DialectIndex. */
+	inc_rfc1001_len(work->response_buf, 4);
 	neg_rsp->hdr.Status.CifsError = STATUS_SUCCESS;
 
-	neg_rsp->hdr.Command = SMB_COM_NEGOTIATE;
-	*(__le32 *)neg_rsp->hdr.Protocol = SMB1_PROTO_NUMBER;
-	neg_rsp->hdr.Flags = SMBFLG_RESPONSE;
-	neg_rsp->hdr.Flags2 = SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS |
-		SMBFLG2_EXT_SEC | SMBFLG2_IS_LONG_NAME;
-
 	neg_rsp->hdr.WordCount = 1;
 	neg_rsp->DialectIndex = cpu_to_le16(work->conn->dialect);
 	neg_rsp->ByteCount = 0;
@@ -473,24 +564,13 @@ int ksmbd_smb_negotiate_common(struct ksmbd_work *work, unsigned int command)
 		ksmbd_negotiate_smb_dialect(work->request_buf);
 	ksmbd_debug(SMB, "conn->dialect 0x%x\n", conn->dialect);
 
-	if (command == SMB2_NEGOTIATE_HE) {
-		struct smb2_hdr *smb2_hdr = smb2_get_msg(work->request_buf);
-
-		if (smb2_hdr->ProtocolId != SMB2_PROTO_NUMBER) {
-			ksmbd_debug(SMB, "Downgrade to SMB1 negotiation\n");
-			command = SMB_COM_NEGOTIATE;
-		}
-	}
-
 	if (command == SMB2_NEGOTIATE_HE) {
 		ret = smb2_handle_negotiate(work);
-		init_smb2_neg_rsp(work);
 		return ret;
 	}
 
 	if (command == SMB_COM_NEGOTIATE) {
 		if (__smb2_negotiate(conn)) {
-			conn->need_neg = true;
 			init_smb3_11_server(conn);
 			init_smb2_neg_rsp(work);
 			ksmbd_debug(SMB, "Upgrade to SMB2 negotiation\n");

fs/ksmbd/smb_common.h

@@ -427,7 +427,7 @@ bool ksmbd_smb_request(struct ksmbd_conn *conn);
 
 int ksmbd_lookup_dialect_by_id(__le16 *cli_dialects, __le16 dialects_count);
 
-int ksmbd_init_smb_server(struct ksmbd_work *work);
+void ksmbd_init_smb_server(struct ksmbd_work *work);
 
 struct ksmbd_kstat;
 int ksmbd_populate_dot_dotdot_entries(struct ksmbd_work *work,