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, 18 insertions, 7 deletions

diff --git a/src/providers/krb5/krb5_common.c b/src/providers/krb5/krb5_common.c
index c78f0e60c..fbc308895 100644
--- a/src/providers/krb5/krb5_common.c
+++ b/src/providers/krb5/krb5_common.c
@@ -158,6 +158,7 @@ errno_t write_krb5info_file(const char *realm, const char *server,
     TALLOC_CTX *tmp_ctx = NULL;
     const char *name_tmpl = NULL;
     int server_len;
+    ssize_t written;
 
     if (realm == NULL || *realm == '\0' || server == NULL || *server == '\0' ||
         service == NULL || service == '\0') {
@@ -203,14 +204,24 @@ errno_t write_krb5info_file(const char *realm, const char *server,
         goto done;
     }
 
-    ret = write(fd, server, server_len);
-    if (ret == -1) {
-        DEBUG(1, ("write failed [%d][%s].\n", errno, strerror(errno)));
-        goto done;
+    written = 0;
+    while (written < server_len) {
+        ret = write(fd, server+written, server_len-written);
+        if (ret == -1) {
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
+            }
+            DEBUG(1, ("write failed [%d][%s].\n", errno, strerror(errno)));
+            goto done;
+        }
+        else {
+            written += ret;
+        }
     }
-    if (ret != server_len) {
-        DEBUG(1, ("Partial write occured, this should never happen.\n"));
-        ret = EINTR;
+
+    if (written != server_len) {
+        DEBUG(1, ("Write error, wrote [%d] bytes, expected [%d]\n",
+                   written, server_len));
         goto done;
     }