[PATCH] lib: fix handling of -ve read returns

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

Coverity Scan 7.5.0 picked up two identical issues where
the -ve read returns were never being detected and so the
code was not going to handle EINTR or EAGAIN errors
correctly.  Re-worked the code in both places to work
as intended.

Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 src/lib/src/fwts_acpi_tables.c | 22 ++++++++++++++--------
 src/lib/src/fwts_pipeio.c      | 28 ++++++++++++++--------------
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/src/lib/src/fwts_acpi_tables.c b/src/lib/src/fwts_acpi_tables.c
index 291c59d..343f849 100644
--- a/src/lib/src/fwts_acpi_tables.c
+++ b/src/lib/src/fwts_acpi_tables.c
@@ -598,26 +598,32 @@ static int fwts_acpi_load_tables_from_acpidump(fwts_framework *fw)
 static uint8_t *fwts_acpi_load_table_from_file(const int fd, size_t *length)
 {
 	uint8_t *ptr = NULL;
-	ssize_t n;
 	size_t size = 0;
 	char buffer[4096];
 
 	*length = 0;
 
-	while ((n = read(fd, buffer, sizeof(buffer))) > 0) {
+	for (;;) {
+		ssize_t n = read(fd, buffer, sizeof(buffer));
+		uint8_t *tmp;
+
+		if (n == 0)
+			break;
 		if (n < 0) {
 			if (errno != EINTR && errno != EAGAIN) {
 				fwts_low_free(ptr);
 				return NULL;
 			}
+			continue;
 		}
-		else {
-			ptr = (uint8_t*)fwts_low_realloc(ptr, size + n + 1);
-			if (ptr == NULL)
-				return NULL;
-			memcpy(ptr + size, buffer, n);
-			size += n;
+
+		if ((tmp = (uint8_t*)fwts_low_realloc(ptr, size + n + 1)) == NULL) {
+			free(ptr);
+			return NULL;
 		}
+		ptr = tmp;
+		memcpy(ptr + size, buffer, n);
+		size += n;
 	}
 	*length = size;
 	return ptr;
diff --git a/src/lib/src/fwts_pipeio.c b/src/lib/src/fwts_pipeio.c
index df07295..fe8e786 100644
--- a/src/lib/src/fwts_pipeio.c
+++ b/src/lib/src/fwts_pipeio.c
@@ -83,33 +83,33 @@ char *fwts_pipe_read(const int fd, ssize_t *length)
 {
 	char *ptr = NULL;
 	char buffer[8192];
-	ssize_t n;
 	ssize_t size = 0;
 	*length = 0;
 
 	ptr = NULL;
 
-	while ((n = read(fd, buffer, sizeof(buffer))) > 0) {
+	for (;;) {
+		ssize_t n = read(fd, buffer, sizeof(buffer));
+		char *tmp;
+
+		if (n == 0)
+			break;
 		if (n < 0) {
 			if (errno != EINTR && errno != EAGAIN) {
 				free(ptr);
 				return NULL;
 			}
+			continue;
 		}
-		else {
-			char *new_ptr;
-
-			new_ptr = realloc(ptr, size + n + 1);
-			if (new_ptr == NULL) {
-				free(ptr);
-				return NULL;
-			} else
-				ptr = new_ptr;
 
-			memcpy(ptr + size, buffer, n);
-			size += n;
-			*(ptr+size) = 0;
+		if ((tmp = realloc(ptr, size + n + 1)) == NULL) {
+			free(ptr);
+			return NULL;
 		}
+		ptr = tmp;
+		memcpy(ptr + size, buffer, n);
+		size += n;
+		*(ptr+size) = 0;
 	}
 	*length = size;
 	return ptr;
-- 
2.0.1