treewide: sanitize loop_write

loop_write() didn't follow the usual systemd rules and returned status
partially in errno and required extensive checks from callers. Some of
the callers dealt with this properly, but many did not, treating
partial writes as successful. Simplify things by conforming to usual rules.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/shared/util.c b/src/shared/util.c
index ff8835b72d..26a4f72b43 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -2292,13 +2292,15 @@ ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) {
         return n;
 }
 
-ssize_t loop_write(int fd, const void *buf, size_t nbytes, bool do_poll) {
+int loop_write(int fd, const void *buf, size_t nbytes, bool do_poll) {
         const uint8_t *p = buf;
         ssize_t n = 0;
 
         assert(fd >= 0);
         assert(buf);
 
+        errno = 0;
+
         while (nbytes > 0) {
                 ssize_t k;
 
@@ -2317,14 +2319,15 @@ ssize_t loop_write(int fd, const void *buf, size_t nbytes, bool do_poll) {
                 }
 
                 if (k <= 0)
-                        return n > 0 ? n : (k < 0 ? -errno : 0);
+                        /* We were not done yet, and a write error occured. */
+                        return errno ? -errno : -EIO;
 
                 p += k;
                 nbytes -= k;
                 n += k;
         }
 
-        return n;
+        return 0;
 }
 
 int parse_size(const char *t, off_t base, off_t *size) {