smb3: Replace smb2pdu 1-element arrays with flex-arrays

commit eb3e28c upstream.

The kernel is globally removing the ambiguous 0-length and 1-element
arrays in favor of flexible arrays, so that we can gain both compile-time
and run-time array bounds checking[1].

Replace the trailing 1-element array with a flexible array in the
following structures:

	struct smb2_err_rsp
	struct smb2_tree_connect_req
	struct smb2_negotiate_rsp
	struct smb2_sess_setup_req
	struct smb2_sess_setup_rsp
	struct smb2_read_req
	struct smb2_read_rsp
	struct smb2_write_req
	struct smb2_write_rsp
	struct smb2_query_directory_req
	struct smb2_query_directory_rsp
	struct smb2_set_info_req
	struct smb2_change_notify_rsp
	struct smb2_create_rsp
	struct smb2_query_info_req
	struct smb2_query_info_rsp

Replace the trailing 1-element array with a flexible array, but leave
the existing structure padding:

	struct smb2_file_all_info
	struct smb2_lock_req

Adjust all related size calculations to match the changes to sizeof().

No machine code output or .data section differences are produced after
these changes.

[1] For lots of details, see both:
    https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
    https://people.kernel.org/kees/bounded-flexible-arrays-in-c

Cc: Steve French <sfrench@samba.org>
Cc: Paulo Alcantara <pc@cjr.nz>
Cc: Ronnie Sahlberg <lsahlber@redhat.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/smb/client/smb2file.c

@@ -34,7 +34,7 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov)
 		len = (u32)err->ErrorContextCount * (offsetof(struct smb2_error_context_rsp,
 							      ErrorContextData) +
 						     sizeof(struct smb2_symlink_err_rsp));
-		if (le32_to_cpu(err->ByteCount) < len || iov->iov_len < len + sizeof(*err))
+		if (le32_to_cpu(err->ByteCount) < len || iov->iov_len < len + sizeof(*err) + 1)
 			return ERR_PTR(-EINVAL);
 
 		p = (struct smb2_error_context_rsp *)err->ErrorData;

fs/smb/client/smb2misc.c

@@ -113,7 +113,7 @@ static __u32 get_neg_ctxt_len(struct smb2_hdr *hdr, __u32 len,
 	} else if (nc_offset + 1 == non_ctxlen) {
 		cifs_dbg(FYI, "no SPNEGO security blob in negprot rsp\n");
 		size_of_pad_before_neg_ctxts = 0;
-	} else if (non_ctxlen == SMB311_NEGPROT_BASE_SIZE)
+	} else if (non_ctxlen == SMB311_NEGPROT_BASE_SIZE + 1)
 		/* has padding, but no SPNEGO blob */
 		size_of_pad_before_neg_ctxts = nc_offset - non_ctxlen + 1;
 	else

fs/smb/client/smb2ops.c

@@ -5764,7 +5764,7 @@ struct smb_version_values smb20_values = {
 	.header_size = sizeof(struct smb2_hdr),
 	.header_preamble_size = 0,
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -5786,7 +5786,7 @@ struct smb_version_values smb21_values = {
 	.header_size = sizeof(struct smb2_hdr),
 	.header_preamble_size = 0,
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -5807,7 +5807,7 @@ struct smb_version_values smb3any_values = {
 	.header_size = sizeof(struct smb2_hdr),
 	.header_preamble_size = 0,
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -5828,7 +5828,7 @@ struct smb_version_values smbdefault_values = {
 	.header_size = sizeof(struct smb2_hdr),
 	.header_preamble_size = 0,
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -5849,7 +5849,7 @@ struct smb_version_values smb30_values = {
 	.header_size = sizeof(struct smb2_hdr),
 	.header_preamble_size = 0,
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -5870,7 +5870,7 @@ struct smb_version_values smb302_values = {
 	.header_size = sizeof(struct smb2_hdr),
 	.header_preamble_size = 0,
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -5891,7 +5891,7 @@ struct smb_version_values smb311_values = {
 	.header_size = sizeof(struct smb2_hdr),
 	.header_preamble_size = 0,
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,

fs/smb/client/smb2pdu.c

@@ -1386,7 +1386,7 @@ SMB2_sess_sendreceive(struct SMB2_sess_data *sess_data)
 
 	/* Testing shows that buffer offset must be at location of Buffer[0] */
 	req->SecurityBufferOffset =
-		cpu_to_le16(sizeof(struct smb2_sess_setup_req) - 1 /* pad */);
+		cpu_to_le16(sizeof(struct smb2_sess_setup_req));
 	req->SecurityBufferLength = cpu_to_le16(sess_data->iov[1].iov_len);
 
 	memset(&rqst, 0, sizeof(struct smb_rqst));
@@ -1905,8 +1905,7 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 	iov[0].iov_len = total_len - 1;
 
 	/* Testing shows that buffer offset must be at location of Buffer[0] */
-	req->PathOffset = cpu_to_le16(sizeof(struct smb2_tree_connect_req)
-			- 1 /* pad */);
+	req->PathOffset = cpu_to_le16(sizeof(struct smb2_tree_connect_req));
 	req->PathLength = cpu_to_le16(unc_path_len - 2);
 	iov[1].iov_base = unc_path;
 	iov[1].iov_len = unc_path_len;
@@ -3796,7 +3795,7 @@ SMB2_change_notify(const unsigned int xid, struct cifs_tcon *tcon,
 			ses->Suid, (u8)watch_tree, completion_filter);
 		/* validate that notify information is plausible */
 		if ((rsp_iov.iov_base == NULL) ||
-		    (rsp_iov.iov_len < sizeof(struct smb2_change_notify_rsp)))
+		    (rsp_iov.iov_len < sizeof(struct smb2_change_notify_rsp) + 1))
 			goto cnotify_exit;
 
 		smb_rsp = (struct smb2_change_notify_rsp *)rsp_iov.iov_base;
@@ -5009,7 +5008,7 @@ int SMB2_query_directory_init(const unsigned int xid,
 	memcpy(bufptr, &asteriks, len);
 
 	req->FileNameOffset =
-		cpu_to_le16(sizeof(struct smb2_query_directory_req) - 1);
+		cpu_to_le16(sizeof(struct smb2_query_directory_req));
 	req->FileNameLength = cpu_to_le16(len);
 	/*
 	 * BB could be 30 bytes or so longer if we used SMB2 specific
@@ -5205,8 +5204,7 @@ SMB2_set_info_init(struct cifs_tcon *tcon, struct TCP_Server_Info *server,
 	req->VolatileFileId = volatile_fid;
 	req->AdditionalInformation = cpu_to_le32(additional_info);
 
-	req->BufferOffset =
-			cpu_to_le16(sizeof(struct smb2_set_info_req) - 1);
+	req->BufferOffset = cpu_to_le16(sizeof(struct smb2_set_info_req));
 	req->BufferLength = cpu_to_le32(*size);
 
 	memcpy(req->Buffer, *data, *size);
@@ -5440,9 +5438,9 @@ build_qfs_info_req(struct kvec *iov, struct cifs_tcon *tcon,
 	req->VolatileFileId = volatile_fid;
 	/* 1 for pad */
 	req->InputBufferOffset =
-			cpu_to_le16(sizeof(struct smb2_query_info_req) - 1);
+			cpu_to_le16(sizeof(struct smb2_query_info_req));
 	req->OutputBufferLength = cpu_to_le32(
-		outbuf_len + sizeof(struct smb2_query_info_rsp) - 1);
+		outbuf_len + sizeof(struct smb2_query_info_rsp));
 
 	iov->iov_base = (char *)req;
 	iov->iov_len = total_len;

fs/smb/client/smb2pdu.h

@@ -57,7 +57,7 @@ struct smb2_rdma_crypto_transform {
 #define COMPOUND_FID 0xFFFFFFFFFFFFFFFFULL
 
 #define SMB2_SYMLINK_STRUCT_SIZE \
-	(sizeof(struct smb2_err_rsp) - 1 + sizeof(struct smb2_symlink_err_rsp))
+	(sizeof(struct smb2_err_rsp) + sizeof(struct smb2_symlink_err_rsp))
 
 #define SYMLINK_ERROR_TAG 0x4c4d5953
 

fs/smb/common/smb2pdu.h

@@ -189,7 +189,7 @@ struct smb2_err_rsp {
 	__u8   ErrorContextCount;
 	__u8   Reserved;
 	__le32 ByteCount;  /* even if zero, at least one byte follows */
-	__u8   ErrorData[1];  /* variable length */
+	__u8   ErrorData[];  /* variable length */
 } __packed;
 
 #define SMB3_AES_CCM_NONCE 11
@@ -330,7 +330,7 @@ struct smb2_tree_connect_req {
 	__le16 Flags;		/* Flags in SMB3.1.1 */
 	__le16 PathOffset;
 	__le16 PathLength;
-	__u8   Buffer[1];	/* variable length */
+	__u8   Buffer[];	/* variable length */
 } __packed;
 
 /* Possible ShareType values */
@@ -617,7 +617,7 @@ struct smb2_negotiate_rsp {
 	__le16 SecurityBufferOffset;
 	__le16 SecurityBufferLength;
 	__le32 NegotiateContextOffset;	/* Pre:SMB3.1.1 was reserved/ignored */
-	__u8   Buffer[1];	/* variable length GSS security buffer */
+	__u8   Buffer[];	/* variable length GSS security buffer */
 } __packed;
 
 
@@ -638,7 +638,7 @@ struct smb2_sess_setup_req {
 	__le16 SecurityBufferOffset;
 	__le16 SecurityBufferLength;
 	__le64 PreviousSessionId;
-	__u8   Buffer[1];	/* variable length GSS security buffer */
+	__u8   Buffer[];	/* variable length GSS security buffer */
 } __packed;
 
 /* Currently defined SessionFlags */
@@ -655,7 +655,7 @@ struct smb2_sess_setup_rsp {
 	__le16 SessionFlags;
 	__le16 SecurityBufferOffset;
 	__le16 SecurityBufferLength;
-	__u8   Buffer[1];	/* variable length GSS security buffer */
+	__u8   Buffer[];	/* variable length GSS security buffer */
 } __packed;
 
 
@@ -737,7 +737,7 @@ struct smb2_read_req {
 	__le32 RemainingBytes;
 	__le16 ReadChannelInfoOffset;
 	__le16 ReadChannelInfoLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 /* Read flags */
@@ -752,7 +752,7 @@ struct smb2_read_rsp {
 	__le32 DataLength;
 	__le32 DataRemaining;
 	__le32 Flags;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 
@@ -776,7 +776,7 @@ struct smb2_write_req {
 	__le16 WriteChannelInfoOffset;
 	__le16 WriteChannelInfoLength;
 	__le32 Flags;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_write_rsp {
@@ -787,7 +787,7 @@ struct smb2_write_rsp {
 	__le32 DataLength;
 	__le32 DataRemaining;
 	__u32  Reserved2;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 
@@ -834,7 +834,10 @@ struct smb2_lock_req {
 	__u64  PersistentFileId;
 	__u64  VolatileFileId;
 	/* Followed by at least one */
-	struct smb2_lock_element locks[1];
+	union {
+		struct smb2_lock_element lock;
+		DECLARE_FLEX_ARRAY(struct smb2_lock_element, locks);
+	};
 } __packed;
 
 struct smb2_lock_rsp {
@@ -888,15 +891,15 @@ struct smb2_query_directory_req {
 	__le16 FileNameOffset;
 	__le16 FileNameLength;
 	__le32 OutputBufferLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_query_directory_rsp {
 	struct smb2_hdr hdr;
 	__le16 StructureSize; /* Must be 9 */
 	__le16 OutputBufferOffset;
 	__le32 OutputBufferLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 /*
@@ -919,7 +922,7 @@ struct smb2_set_info_req {
 	__le32 AdditionalInformation;
 	__u64  PersistentFileId;
 	__u64  VolatileFileId;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_set_info_rsp {
@@ -974,7 +977,7 @@ struct smb2_change_notify_rsp {
 	__le16	StructureSize;  /* Must be 9 */
 	__le16	OutputBufferOffset;
 	__le32	OutputBufferLength;
-	__u8	Buffer[1]; /* array of file notify structs */
+	__u8	Buffer[]; /* array of file notify structs */
 } __packed;
 
 
@@ -1180,7 +1183,7 @@ struct smb2_create_rsp {
 	__u64  VolatileFileId;
 	__le32 CreateContextsOffset;
 	__le32 CreateContextsLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct create_posix {
@@ -1524,15 +1527,15 @@ struct smb2_query_info_req {
 	__le32 Flags;
 	__u64  PersistentFileId;
 	__u64  VolatileFileId;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_query_info_rsp {
 	struct smb2_hdr hdr;
 	__le16 StructureSize; /* Must be 9 */
 	__le16 OutputBufferOffset;
 	__le32 OutputBufferLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 /*
@@ -1593,7 +1596,10 @@ struct smb2_file_all_info { /* data block encoding of response to level 18 */
 	__le32 Mode;
 	__le32 AlignmentRequirement;
 	__le32 FileNameLength;
-	char   FileName[1];
+	union {
+		char __pad;	/* Legacy structure padding */
+		DECLARE_FLEX_ARRAY(char, FileName);
+	};
 } __packed; /* level 18 Query */
 
 struct smb2_file_eof_info { /* encoding of request for level 10 */

fs/smb/server/smb2ops.c

@@ -26,7 +26,7 @@ static struct smb_version_values smb21_server_values = {
 	.unlock_lock_type = SMB2_LOCKFLAG_UNLOCK,
 	.header_size = sizeof(struct smb2_hdr),
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -52,7 +52,7 @@ static struct smb_version_values smb30_server_values = {
 	.unlock_lock_type = SMB2_LOCKFLAG_UNLOCK,
 	.header_size = sizeof(struct smb2_hdr),
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -79,7 +79,7 @@ static struct smb_version_values smb302_server_values = {
 	.unlock_lock_type = SMB2_LOCKFLAG_UNLOCK,
 	.header_size = sizeof(struct smb2_hdr),
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,
@@ -106,7 +106,7 @@ static struct smb_version_values smb311_server_values = {
 	.unlock_lock_type = SMB2_LOCKFLAG_UNLOCK,
 	.header_size = sizeof(struct smb2_hdr),
 	.max_header_size = MAX_SMB2_HDR_SIZE,
-	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.read_rsp_size = sizeof(struct smb2_read_rsp),
 	.lock_cmd = SMB2_LOCK,
 	.cap_unix = 0,
 	.cap_nt_find = SMB2_NT_FIND,

fs/smb/server/smb2pdu.c

@@ -294,8 +294,7 @@ int init_smb2_neg_rsp(struct ksmbd_work *work)
 	if (server_conf.signing == KSMBD_CONFIG_OPT_MANDATORY)
 		rsp->SecurityMode |= SMB2_NEGOTIATE_SIGNING_REQUIRED_LE;
 	err = ksmbd_iov_pin_rsp(work, rsp,
-				sizeof(struct smb2_negotiate_rsp) -
-				sizeof(rsp->Buffer) + AUTH_GSS_LENGTH);
+				sizeof(struct smb2_negotiate_rsp) + AUTH_GSS_LENGTH);
 	if (err)
 		return err;
 	conn->use_spnego = true;
@@ -1263,9 +1262,8 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
 
 	if (!rc)
 		rc = ksmbd_iov_pin_rsp(work, rsp,
-				       sizeof(struct smb2_negotiate_rsp) -
-					sizeof(rsp->Buffer) +
-					AUTH_GSS_LENGTH + neg_ctxt_len);
+				       sizeof(struct smb2_negotiate_rsp) +
+				       AUTH_GSS_LENGTH + neg_ctxt_len);
 	if (rc < 0)
 		smb2_set_err_rsp(work);
 	return rc;