sys/linux, executor: Add KSMBD subsystem support

Introduces a new pseudo-syscall `syz_ksmbd_send_req` to fuzzing of
the KSMBD module. The added functionality enables sending custom SMB2/3
requests to the KSMBD server on 127.0.0.1:445.

Cc: [email protected]
Cc: [email protected]
Cc: Namjae Jeon <[email protected]>
Signed-off-by: Yunseong Kim <[email protected]>

executor/common_linux.h

@@ -5833,3 +5833,64 @@ static long syz_pidfd_open(volatile long pid, volatile long flags)
 }
 
 #endif
+
+#if SYZ_EXECUTOR || __NR_syz_ksmbd_send_req
+#include <netinet/in.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#define KSMBD_BUF_SIZE 16000
+
+static long syz_ksmbd_send_req(volatile long a0, volatile long a1, volatile long a2, volatile long a3)
+{
+	int sockfd;
+	int packet_reqlen;
+	int errno;
+	struct sockaddr_in serv_addr;
+	char packet_req[KSMBD_BUF_SIZE]; // max frame size
+
+	debug("[*]{syz_ksmbd_send_req} entered ksmbd send...\n");
+
+	if (a0 == 0 || a1 == 0) {
+		debug("[!]{syz_ksmbd_send_req} param empty\n");
+		return -7;
+	}
+
+	sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (sockfd < 0) {
+		debug("[!]{syz_ksmbd_send_req} failed to create socket\n");
+		return -1;
+	}
+
+	memset(&serv_addr, '\0', sizeof(serv_addr));
+	serv_addr.sin_family = AF_INET;
+	serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
+	serv_addr.sin_port = htons(445);
+
+	errno = connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
+	if (errno < 0) {
+		debug("[!]{syz_ksmbd_send_req} failed to connect (err: %d)\n", errno);
+		return errno ^ 0xff80000;
+	}
+
+	// prepend kcov handle to packet
+	packet_reqlen = a1 + 8 > KSMBD_BUF_SIZE ? KSMBD_BUF_SIZE - 8 : a1;
+	*(unsigned long*)packet_req = procid + 1;
+	memcpy(packet_req + 8, (char*)a0, packet_reqlen);
+
+	if (write(sockfd, (char*)packet_req, packet_reqlen + 8) < 0)
+		return -4;
+
+	if (read(sockfd, (char*)a2, a3) < 0)
+		return -5;
+
+	if (close(sockfd) < 0)
+		return -6;
+
+	debug("[+]{syz_ksmbd_send_req} successfully returned\n");
+
+	return 0;
+}
+#endif

pkg/vminfo/linux_syscalls.go

@@ -103,6 +103,7 @@ var linuxSyscallChecks = map[string]func(*checkContext, *prog.Syscall) string{
 	"syz_socket_connect_nvme_tcp": linuxSyzSocketConnectNvmeTCPSupported,
 	"syz_pidfd_open":              alwaysSupported,
 	"syz_create_resource":         alwaysSupported,
+	"syz_ksmbd_send_req":          alwaysSupported,
 }
 
 func linuxSyzOpenDevSupported(ctx *checkContext, call *prog.Syscall) string {

sys/linux/ksmbd.txt

@@ -0,0 +1,168 @@
+include <linux/ip.h>
+include <linux/ipv6.h>
+include <linux/route.h>
+include <uapi/linux/if_arp.h>
+include <uapi/linux/netfilter_ipv6/ip6_tables.h>
+include <uapi/linux/wireless.h>
+include <uapi/linux/in.h>
+
+sync_id {
+	ProcessId	int32
+	TreeId		int32
+} [packed]
+
+_union_smb_req_id [
+	sync_id		sync_id
+	async_id	int64
+]
+
+negotiate_message {
+	Signature			array[int8, 8]
+#  NtLmNegotiate = 1
+	MessageType			int32
+	NegotiateFlags			int32
+# MBZ unless SMB3.02 or later
+	DomainName_Length		len[DomainString, int16]
+	DomainName_MaximumLength	len[DomainString, int16]
+	DomainName_Offset		offsetof[DomainString, int32]
+# RFC 1001 and ASCII
+	WorkstationName_Length		len[Workstationname_Buffer, int16]
+	WorkstationName_MaximumLength	len[Workstationname_Buffer, int16]
+	WorkstationName_Offset		offsetof[Workstationname_Buffer, int32]
+
+# struct security_buffer for version info not present since we
+# do not set the version is present flag
+	DomainString			string
+
+# followed by WorkstationString
+	Workstationname_Buffer		string
+} [packed]
+
+_smb2_hdr_pre {
+	ProtocolId	const[0xfe534d42, int32be]
+	StructureSize	const[0x40, int16]
+	CreditCharge	int16
+	Status		int32
+} [packed]
+
+_smb2_hdr_post {
+	CreditRequest	int16
+	Flags		int32
+	NextCommand	int32
+	MessageId	int64
+	Id		_union_smb_req_id
+	SessionId	int64
+	Signature	array[int8, 16]
+} [packed]
+
+#_smb3_hdr_pre {
+#	ProtocolId	const[0xfe534d42, int32be]
+#	StructureSize	const[0x40, int16]
+#	CreditCharge	int16
+#	ChannelSequence	int16
+#	Reserved	int16
+#} [packed]
+
+#_smb3_hdr_post {
+#	CreditRequest	int16
+#	Flags		int32
+#	NextCommand	int32
+#	MessageId	int64
+#	Id		_union_smb_req_id
+#	SessionId	int64
+#	Signature	array[int8, 16]
+#} [packed]
+
+smb2_negotiate_req {
+	_hdr_pre		_smb2_hdr_pre
+	Command			const[0x0, int16]
+	_hdr_post		_smb2_hdr_post
+	StructureSize		const[36, int16]
+	DialectCount		len[Dialects, int16]
+	SecurityMode		int16
+	Reserved		int16
+	Capabilities		int32
+	ClientGUID		array[int8, 16]
+
+# In SMB3.02 and earlier next three were MBZ le64 ClientStartTime
+	NegotiateContextOffset	int32
+	NegotiateContextCount	int16
+	Reserved2		int16
+	Dialects		buffer[in]
+} [packed]
+
+smb2_sess_setup_req {
+	_hdr_pre		_smb2_hdr_pre
+	Command			const[0x1, int16]
+	_hdr_post		_smb2_hdr_post
+	StructureSize		const[25, int16]
+	Flags			int8
+	SecurityMode		int8
+	Capabilities		int32
+	Channel			int32
+	SecurityBufferOffset	offsetof[Buffer, int16]
+	SecurityBufferLength	len[Buffer, int16]
+	PreviousSessionId	int64
+
+# variable length GSS security buffer
+	Buffer			negotiate_message
+} [packed]
+
+smb2_echo_req {
+	_hdr_pre	_smb2_hdr_pre
+	Command		const[0xd, int16]
+	_hdr_post	_smb2_hdr_post
+	StructureSize2	const[4, int16]
+	Reserved	int16
+} [packed]
+
+smbd_buffer_descriptor_v1 {
+	offset			int64
+	token			int32
+	length			int32
+# followed by Smbd_Buffer
+	smb2_read_req_buffer	string
+} [packed]
+
+smb2_read_req {
+	_hdr_pre		_smb2_hdr_pre
+	Command			const[0x8, int16]
+	_hdr_post		_smb2_hdr_post
+# Must be 49
+	StructureSize		const[49, int16]
+# offset from start of SMB2 header to place read
+	Padding			int8
+# MBZ unless SMB3.02 or later
+	Flags			int8
+	Length			int32
+	Offset			int64
+	PersistentFileId	int64
+	VolatileFileId		int64
+	MinimumCount		int32
+# MBZ except for SMB3 or later
+	Channel			int32
+	RemainingBytes		int32
+	ReadChannelInfoOffset	offsetof[Buffer, int16]
+	ReadChannelInfoLength	len[Buffer, int16]
+	Buffer			smbd_buffer_descriptor_v1
+} [packed]
+
+_union_smb2_req [
+	smb2_negotiate_req	smb2_negotiate_req
+	smb2_sess_setup_req	smb2_sess_setup_req
+	smb2_echo_req		smb2_echo_req
+	smb2_read_req		smb2_read_req
+] [varlen]
+
+smb2_req {
+	req_base	_union_smb2_req
+	req_andx1	optional[_union_smb2_req]
+	req_andx2	optional[_union_smb2_req]
+} [packed]
+
+smb2_req_pdu {
+	_pdu_size	len[req, int32be]
+	req		smb2_req
+} [packed]
+
+syz_ksmbd_send_req(req_packet ptr[in, smb2_req_pdu], req_len len[req_packet], res_packet buffer[out], res_len len[res_packet])