diff --git a/lib/crypto_backend/crypto_storage.c b/lib/crypto_backend/crypto_storage.c
index 6c8f991a..f06b10f0 100644
--- a/lib/crypto_backend/crypto_storage.c
+++ b/lib/crypto_backend/crypto_storage.c
@@ -261,7 +261,7 @@ int crypt_storage_init(struct crypt_storage **ctx,
 	}
 
 	s->sector_size = sector_size;
-	s->iv_shift = large_iv ? int_log2(sector_size) - SECTOR_SHIFT : 0;
+	s->iv_shift = large_iv ? (unsigned)int_log2(sector_size) - SECTOR_SHIFT : 0;
 
 	*ctx = s;
 	return 0;
diff --git a/lib/crypto_backend/utf8.c b/lib/crypto_backend/utf8.c
index c13e9538..339d4ca9 100644
--- a/lib/crypto_backend/utf8.c
+++ b/lib/crypto_backend/utf8.c
@@ -230,6 +230,7 @@ static size_t utf16_encode_unichar(char16_t *out, char32_t c)
 		return 1;
 
 	case 0x10000U ... 0x10ffffU:
+		/* coverity[overflow_const:FALSE] */
 		c -= 0x10000U;
 		out[0] = htole16((c >> 10) + 0xd800U);
 		out[1] = htole16((c & 0x3ffU) + 0xdc00U);
diff --git a/lib/luks2/luks2_luks1_convert.c b/lib/luks2/luks2_luks1_convert.c
index 95132172..1a753f35 100644
--- a/lib/luks2/luks2_luks1_convert.c
+++ b/lib/luks2/luks2_luks1_convert.c
@@ -621,6 +621,10 @@ int LUKS2_luks1_to_luks2(struct crypt_device *cd, struct luks_phdr *hdr1, struct
 	if (max_size < required_size)
 		max_size = required_size;
 
+	/* fix coverity false positive integer underflow */
+	if (max_size < 2 * LUKS2_HDR_16K_LEN)
+		return -EINVAL;
+
 	r = json_luks1_object(hdr1, &jobj, max_size - 2 * LUKS2_HDR_16K_LEN);
 	if (r < 0)
 		return r;
diff --git a/lib/tcrypt/tcrypt.c b/lib/tcrypt/tcrypt.c
index 9ae7aaa1..4b455515 100644
--- a/lib/tcrypt/tcrypt.c
+++ b/lib/tcrypt/tcrypt.c
@@ -1070,7 +1070,7 @@ uint64_t TCRYPT_get_iv_offset(struct crypt_device *cd,
 			      struct tcrypt_phdr *hdr,
 			      struct crypt_params_tcrypt *params)
 {
-	uint64_t iv_offset;
+	uint64_t iv_offset, partition_offset;
 
 	if (params->mode && !strncmp(params->mode, "xts", 3))
 		iv_offset = TCRYPT_get_data_offset(cd, hdr, params);
@@ -1079,8 +1079,14 @@ uint64_t TCRYPT_get_iv_offset(struct crypt_device *cd,
 	else
 		iv_offset = hdr->d.mk_offset / SECTOR_SIZE;
 
-	if (params->flags & CRYPT_TCRYPT_SYSTEM_HEADER)
-		iv_offset += crypt_dev_partition_offset(device_path(crypt_data_device(cd)));
+	if (params->flags & CRYPT_TCRYPT_SYSTEM_HEADER) {
+		partition_offset = crypt_dev_partition_offset(device_path(crypt_data_device(cd)));
+		/* FIXME: we need to deal with overflow sooner */
+		if (iv_offset > (UINT64_MAX - partition_offset))
+			iv_offset = UINT64_MAX;
+		else
+			iv_offset += partition_offset;
+	}
 
 	return iv_offset;
 }
diff --git a/lib/utils_io.c b/lib/utils_io.c
index 1c6b456f..da8674c2 100644
--- a/lib/utils_io.c
+++ b/lib/utils_io.c
@@ -22,6 +22,7 @@
  */
 
 #include <errno.h>
+#include <limits.h>
 #include <string.h>
 #include <stdlib.h>
 #include <stdint.h>
@@ -32,10 +33,9 @@
 /* coverity[ -taint_source : arg-1 ] */
 static ssize_t _read_buffer(int fd, void *buf, size_t length, volatile int *quit)
 {
-	size_t read_size = 0;
-	ssize_t r;
+	ssize_t r, read_size = 0;
 
-	if (fd < 0 || !buf)
+	if (fd < 0 || !buf || length > SSIZE_MAX)
 		return -EINVAL;
 
 	do {
@@ -43,12 +43,13 @@ static ssize_t _read_buffer(int fd, void *buf, size_t length, volatile int *quit
 		if (r == -1 && errno != EINTR)
 			return r;
 		if (r > 0) {
-			read_size += (size_t)r;
+			/* coverity[overflow:FALSE] */
+			read_size += r;
 			buf = (uint8_t*)buf + r;
 		}
 		if (r == 0 || (quit && *quit))
-			return (ssize_t)read_size;
-	} while (read_size != length);
+			return read_size;
+	} while ((size_t)read_size != length);
 
 	return (ssize_t)length;
 }
@@ -65,25 +66,25 @@ ssize_t read_buffer_intr(int fd, void *buf, size_t length, volatile int *quit)
 
 static ssize_t _write_buffer(int fd, const void *buf, size_t length, volatile int *quit)
 {
-	size_t write_size = 0;
-	ssize_t w;
+	ssize_t w, write_size = 0;
 
-	if (fd < 0 || !buf || !length)
+	if (fd < 0 || !buf || !length || length > SSIZE_MAX)
 		return -EINVAL;
 
 	do {
-		w = write(fd, buf, length - write_size);
+		w = write(fd, buf, length - (size_t)write_size);
 		if (w < 0 && errno != EINTR)
 			return w;
 		if (w > 0) {
-			write_size += (size_t) w;
+			/* coverity[overflow:FALSE] */
+			write_size += w;
 			buf = (const uint8_t*)buf + w;
 		}
 		if (w == 0 || (quit && *quit))
-			return (ssize_t)write_size;
-	} while (write_size != length);
+			return write_size;
+	} while ((size_t)write_size != length);
 
-	return (ssize_t)write_size;
+	return write_size;
 }
 
 ssize_t write_buffer(int fd, const void *buf, size_t length)
diff --git a/lib/utils_keyring.c b/lib/utils_keyring.c
index 6bd3c48f..08e15c59 100644
--- a/lib/utils_keyring.c
+++ b/lib/utils_keyring.c
@@ -158,7 +158,7 @@ static key_serial_t find_key_by_type_and_desc(const char *type, const char *desc
 	char *newline;
 	size_t buffer_len = 0;
 
-	int n;
+	ssize_t n;
 
 	do {
 		id = request_key(type, desc, NULL, 0);
@@ -171,7 +171,8 @@ static key_serial_t find_key_by_type_and_desc(const char *type, const char *desc
 		return 0;
 
 	while ((n = read(f, buf + buffer_len, sizeof(buf) - buffer_len - 1)) > 0) {
-		buffer_len += n;
+		/* coverity[overflow:FALSE] */
+		buffer_len += (size_t)n;
 		buf[buffer_len] = '\0';
 		newline = strchr(buf, '\n');
 		while (newline != NULL && buffer_len != 0) {
diff --git a/src/utils_password.c b/src/utils_password.c
index 70da4b07..32504568 100644
--- a/src/utils_password.c
+++ b/src/utils_password.c
@@ -109,8 +109,10 @@ static int tools_check_password(const char *password)
 static ssize_t read_tty_eol(int fd, char *pass, size_t maxlen)
 {
 	bool eol = false;
-	size_t read_size = 0;
-	ssize_t r;
+	ssize_t r, read_size = 0;
+
+	if (maxlen > SSIZE_MAX)
+		return -EINVAL;
 
 	do {
 		r = read(fd, pass, maxlen - read_size);
@@ -119,12 +121,13 @@ static ssize_t read_tty_eol(int fd, char *pass, size_t maxlen)
 		if (r >= 0) {
 			if (!r || pass[r-1] == '\n')
 				eol = true;
-			read_size += (size_t)r;
+			/* coverity[overflow:FALSE] */
+			read_size += r;
 			pass = pass + r;
 		}
-	} while (!eol && read_size != maxlen);
+	} while (!eol && (size_t)read_size != maxlen);
 
-	return (ssize_t)read_size;
+	return read_size;
 }
 
 /* The pass buffer is zeroed and has trailing \0 already " */
diff --git a/src/utils_reencrypt_luks1.c b/src/utils_reencrypt_luks1.c
index 1e36ad96..9a640f91 100644
--- a/src/utils_reencrypt_luks1.c
+++ b/src/utils_reencrypt_luks1.c
@@ -690,10 +690,13 @@ out:
 	return r;
 }
 
+/* FIXME this function will be replaced with equivalent from lib/utils_io.c */
 static ssize_t read_buf(int fd, void *buf, size_t count)
 {
-	size_t read_size = 0;
-	ssize_t s;
+	ssize_t s, read_size = 0;
+
+	if (count > SSIZE_MAX)
+		return -EINVAL;
 
 	do {
 		/* This expects that partial read is aligned in buffer */
@@ -701,14 +704,17 @@ static ssize_t read_buf(int fd, void *buf, size_t count)
 		if (s == -1 && errno != EINTR)
 			return s;
 		if (s == 0)
-			return (ssize_t)read_size;
+			return read_size;
 		if (s > 0) {
 			if (s != (ssize_t)count)
 				log_dbg("Partial read %zd / %zu.", s, count);
-			read_size += (size_t)s;
+			/* FIXME: temporarily silence coverity INTEGER_OVERFLOW (CWE-190) */
+			if (read_size > SSIZE_MAX - s)
+				return -1;
+			read_size += s;
 			buf = (uint8_t*)buf + s;
 		}
-	} while (read_size != count);
+	} while ((size_t)read_size != count);
 
 	return (ssize_t)count;
 }
@@ -727,6 +733,10 @@ static int copy_data_forward(struct reenc_ctx *rc, int fd_old, int fd_new,
 		.device = tools_get_device_name(rc->device, &backing_file)
 	};
 
+	assert(rc);
+	assert(bytes);
+	assert(buf);
+
 	log_dbg("Reencrypting in forward direction.");
 
 	if (lseek(fd_old, rc->device_offset, SEEK_SET) < 0 ||
@@ -746,19 +756,18 @@ static int copy_data_forward(struct reenc_ctx *rc, int fd_old, int fd_new,
 		if ((rc->device_size - rc->device_offset) < (uint64_t)block_size)
 			block_size = rc->device_size - rc->device_offset;
 		s1 = read_buf(fd_old, buf, block_size);
-		if (s1 < 0 || ((size_t)s1 != block_size &&
-		    (rc->device_offset + s1) != rc->device_size)) {
+		if (s1 < 0 || ((size_t)s1 != block_size)) {
 			log_dbg("Read error, expecting %zu, got %zd.",
 				block_size, s1);
 			goto out;
 		}
 
-		/* If device_size is forced, never write more than limit */
-		if ((s1 + rc->device_offset) > rc->device_size)
-			s1 = rc->device_size - rc->device_offset;
-
+		/*
+		 * FIXME: this may fail with shorter write.
+		 * Replace ir with write_buffer from lib/utils_io.c
+		 */
 		s2 = write(fd_new, buf, s1);
-		if (s2 < 0) {
+		if (s2 < 0 || s2 != s1) {
 			log_dbg("Write error, expecting %zu, got %zd.",
 				block_size, s2);
 			goto out;
@@ -840,6 +849,10 @@ static int copy_data_backward(struct reenc_ctx *rc, int fd_old, int fd_new,
 			goto out;
 		}
 
+		/*
+		 * FIXME: this may fail with shorter write.
+		 * Replace ir with write_buffer from lib/utils_io.c
+		 */
 		s2 = write(fd_new, buf, working_block);
 		if (s2 < 0) {
 			log_dbg("Write error, expecting %zu, got %zd.",
@@ -872,6 +885,11 @@ static void zero_rest_of_device(int fd, size_t block_size, void *buf,
 {
 	ssize_t s1, s2;
 
+	assert(bytes);
+
+	if (*bytes > SSIZE_MAX || !block_size || block_size > SSIZE_MAX)
+		return;
+
 	log_dbg("Zeroing rest of device.");
 
 	if (lseek(fd, offset, SEEK_SET) < 0) {
@@ -884,10 +902,14 @@ static void zero_rest_of_device(int fd, size_t block_size, void *buf,
 
 	while (!quit && *bytes) {
 		if (*bytes < (uint64_t)s1)
-			s1 = *bytes;
+			s1 = (ssize_t)*bytes;
 
+		/*
+		 * FIXME: this may fail with shorter write.
+		 * Replace ir with write_buffer from lib/utils_io.c
+		 */
 		s2 = write(fd, buf, s1);
-		if (s2 != s1) {
+		if (s2 < 0 || s2 != s1) {
 			log_dbg("Write error, expecting %zd, got %zd.",
 				s1, s2);
 			return;
@@ -898,7 +920,7 @@ static void zero_rest_of_device(int fd, size_t block_size, void *buf,
 			return;
 		}
 
-		*bytes -= s2;
+		*bytes -= (uint64_t)s2;
 	}
 }