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

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>

1 files changed, 7 insertions, 9 deletions

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 3bc0aa8a18b2..4982f5e65e13 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1373,7 +1373,7 @@ 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));
@@ -1892,8 +1892,7 @@ 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);
 	iov[1].iov_base = unc_path;
 	iov[1].iov_len = unc_path_len;
@@ -3773,7 +3772,7 @@ 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;
@@ -4966,7 +4965,7 @@ 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
@@ -5162,8 +5161,7 @@ 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);
@@ -5397,9 +5395,9 @@ 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;