libuuid, uuidd: Avoid infinite loop while reading from the socket fd

If for some reason the uuidd daemon or the process calling uuidd
exited unexpectely, the read_all() function would end up looping
forever, either in uuidd or in libuuid.  Fix this terminating the loop
if no data can be read after five tries to read from the file
descriptor.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 16 insertions, 8 deletions

diff --git a/lib/uuid/gen_uuid.c b/lib/uuid/gen_uuid.c
index aa313efe..5893aff3 100644
--- a/lib/uuid/gen_uuid.c
+++ b/lib/uuid/gen_uuid.c
@@ -419,15 +419,19 @@ static ssize_t read_all(int fd, char *buf, size_t count)
 {
 	ssize_t ret;
 	ssize_t c = 0;
+	int tries = 0;
 
 	memset(buf, 0, count);
 	while (count > 0) {
 		ret = read(fd, buf, count);
-		if (ret < 0) {
-			if ((errno == EAGAIN) || (errno == EINTR))
+		if (ret <= 0) {
+			if ((errno == EAGAIN || errno == EINTR || ret == 0) &&
+			    (tries++ < 5))
 				continue;
-			return -1;
+			return c ? c : -1;
 		}
+		if (ret > 0)
+			tries = 0;
 		count -= ret;
 		buf += ret;
 		c += ret;
diff --git a/misc/uuidd.c b/misc/uuidd.c
index 6913bf7e..89bff721 100644
--- a/misc/uuidd.c
+++ b/misc/uuidd.c
@@ -85,19 +85,23 @@ static void create_daemon(void)
 		die("setreuid");
 }
 
-static int read_all(int fd, char *buf, size_t count)
+static ssize_t read_all(int fd, char *buf, size_t count)
 {
 	ssize_t ret;
-	int c = 0;
+	ssize_t c = 0;
+	int tries = 0;
 
 	memset(buf, 0, count);
 	while (count > 0) {
 		ret = read(fd, buf, count);
-		if (ret < 0) {
-			if ((errno == EAGAIN) || (errno == EINTR))
+		if (ret <= 0) {
+			if ((errno == EAGAIN || errno == EINTR || ret == 0) &&
+			    (tries++ < 5))
 				continue;
-			return -1;
+			return c ? c : -1;
 		}
+		if (ret > 0)
+			tries = 0;
 		count -= ret;
 		buf += ret;
 		c += ret;