Properly handle read() and write() throughout the SSSD

We need to guarantee at all times that reads and writes complete
successfully. This means that they must be checked for returning
EINTR and EAGAIN, and all writes must be wrapped in a loop to
ensure that they do not truncate their output.

1 files changed, 9 insertions, 4 deletions

diff --git a/src/util/find_uid.c b/src/util/find_uid.c
index 965966ef3..952aeea4a 100644
--- a/src/util/find_uid.c
+++ b/src/util/find_uid.c
@@ -100,10 +100,15 @@ static errno_t get_uid_from_pid(const pid_t pid, uid_t *uid)
         DEBUG(1, ("open failed [%d][%s].\n", errno, strerror(errno)));
         return errno;
     }
-    ret = read(fd, buf, BUFSIZE);
-    if (ret == -1) {
-        DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
-        return errno;
+
+    while ((ret = read(fd, buf, BUFSIZE)) != 0) {
+        if (ret == -1) {
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
+            }
+            DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
+            return errno;
+        }
     }
 
     ret = close(fd);