cifs: get rid of dup length check in parse_reparse_point()

smb2_compound_op(SMB2_OP_GET_REPARSE) already checks if ioctl response
has a valid reparse data buffer's length, so there's no need to check
it again in parse_reparse_point().

In order to get rid of duplicate check, validate reparse data buffer's
length also in cifs_query_reparse_point().

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Paulo Alcantara

fs/smb/client/cifssmb.c

@@ -2700,11 +2700,12 @@ int cifs_query_reparse_point(const unsigned int xid,
 			     u32 *tag, struct kvec *rsp,
 			     int *rsp_buftype)
 {
+	struct reparse_data_buffer *buf;
 	struct cifs_open_parms oparms;
 	TRANSACT_IOCTL_REQ *io_req = NULL;
 	TRANSACT_IOCTL_RSP *io_rsp = NULL;
 	struct cifs_fid fid;
-	__u32 data_offset, data_count;
+	__u32 data_offset, data_count, len;
 	__u8 *start, *end;
 	int io_rsp_len;
 	int oplock = 0;
@@ -2774,7 +2775,16 @@ int cifs_query_reparse_point(const unsigned int xid,
 		goto error;
 	}
 
-	*tag = le32_to_cpu(((struct reparse_data_buffer *)start)->ReparseTag);
+	data_count = le16_to_cpu(io_rsp->ByteCount);
+	buf = (struct reparse_data_buffer *)start;
+	len = sizeof(*buf);
+	if (data_count < len ||
+	    data_count < le16_to_cpu(buf->ReparseDataLength) + len) {
+		rc = -EIO;
+		goto error;
+	}
+
+	*tag = le32_to_cpu(buf->ReparseTag);
 	rsp->iov_base = io_rsp;
 	rsp->iov_len = io_rsp_len;
 	*rsp_buftype = CIFS_LARGE_BUFFER;

fs/smb/client/smb2ops.c

@@ -2947,18 +2947,6 @@ int parse_reparse_point(struct reparse_data_buffer *buf,
 			u32 plen, struct cifs_sb_info *cifs_sb,
 			bool unicode, struct cifs_open_info_data *data)
 {
-	if (plen < sizeof(*buf)) {
-		cifs_dbg(VFS, "%s: reparse buffer is too small. Must be at least 8 bytes but was %d\n",
-			 __func__, plen);
-		return -EIO;
-	}
-
-	if (plen < le16_to_cpu(buf->ReparseDataLength) + sizeof(*buf)) {
-		cifs_dbg(VFS, "%s: invalid reparse buf length: %d\n",
-			 __func__, plen);
-		return -EIO;
-	}
-
 	data->reparse.buf = buf;
 
 	/* See MS-FSCC 2.1.2 */