diff -rupN cryptsetup-1.7.4.bcp/lib/utils.c cryptsetup-1.7.4/lib/utils.c

--- cryptsetup-1.7.4.bcp/lib/utils.c	2017-10-18 11:39:01.694902755 +0200

+++ cryptsetup-1.7.4/lib/utils.c	2017-10-18 11:48:16.584868357 +0200

@@ -252,21 +252,21 @@ ssize_t write_lseek_blockwise(int fd, in

 		if (!frontPadBuf)

 			goto out;

-		r = read_buffer(fd, frontPadBuf, bsize);

-		if (r < 0 || r != bsize)

-			goto out;

-

 		innerCount = bsize - frontHang;

 		if (innerCount > count)

 			innerCount = count;

+		r = read_buffer(fd, frontPadBuf, bsize);

+		if (r < (frontHang + innerCount))

+			goto out;

+

 		memcpy(frontPadBuf + frontHang, buf, innerCount);

 		if (lseek(fd, offset - frontHang, SEEK_SET) < 0)

 			goto out;

-		r = write_buffer(fd, frontPadBuf, bsize);

-		if (r < 0 || r != bsize)

+		r = write_buffer(fd, frontPadBuf, frontHang + innerCount);

+		if (r != (frontHang + innerCount))

 			goto out;

 		buf = (char*)buf + innerCount;

@@ -311,14 +311,14 @@ ssize_t read_lseek_blockwise(int fd, int

 		if (!frontPadBuf)

 			return ret;

-		r = read_buffer(fd, frontPadBuf, bsize);

-		if (r < 0 || r != bsize)

-			goto out;

-

 		innerCount = bsize - frontHang;

 		if (innerCount > count)

 			innerCount = count;

+		r = read_buffer(fd, frontPadBuf, bsize);

+		if (r < (frontHang + innerCount))

+			goto out;

+

 		memcpy(buf, frontPadBuf + frontHang, innerCount);

 		buf = (char*)buf + innerCount;