Fix handling of partial writes from writev() which can occur with

large output buffers.

diff --git a/plugins/sudoers/sudoreplay.c b/plugins/sudoers/sudoreplay.c
index 2185437bf12021bcde0d54066c969b36cc0f6e90..d1fafbf691c444e5f922e73b4d06cef3028ad175 100644 (file)
--- a/plugins/sudoers/sudoreplay.c
+++ b/plugins/sudoers/sudoreplay.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2014 Todd C. Miller <Todd.Miller@courtesan.com>
+ * Copyright (c) 2009-2015 Todd C. Miller <Todd.Miller@courtesan.com>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -576,13 +576,12 @@ static void
 write_output(int fd, int what, void *v)
 {
     struct write_closure *wc = v;
-    ssize_t nwritten;
-    size_t count, remainder;
+    size_t nwritten;
     unsigned int i;
     debug_decl(write_output, SUDO_DEBUG_UTIL, sudoreplay_debug_instance)
 
     nwritten = writev(STDOUT_FILENO, wc->iov, wc->iovcnt);
-    switch (nwritten) {
+    switch ((ssize_t)nwritten) {
     case -1:
        if (errno != EINTR && errno != EAGAIN)
            sudo_fatal(U_("unable to write to %s"), "stdout");
@@ -590,30 +589,24 @@ write_output(int fd, int what, void *v)
     case 0:
        break;
     default:
-       remainder = wc->nbytes - nwritten;
-       if (remainder == 0) {
+       if (wc->nbytes == nwritten) {
            /* writev completed */
            debug_return;
        }
 
        /* short writev, adjust iov so we can write the remainder. */
-       count = 0;
+       wc->nbytes -= nwritten;
        i = wc->iovcnt;
        while (i--) {
-           count += wc->iov[i].iov_len;
-           if (count == remainder) {
-               wc->iov += i;
-               wc->iovcnt -= i;
-               break;
-           }
-           if (count > remainder) {
-               size_t off = (count - remainder);
-               wc->iov[i].iov_base = (char *)wc->iov[i].iov_base + off;
-               wc->iov[i].iov_len -= off;
-               wc->iov += i;
-               wc->iovcnt -= i;
+           if (wc->iov[0].iov_len > nwritten) {
+               /* Partial write, adjust base and len and reschedule. */
+               wc->iov[0].iov_base = (char *)wc->iov[0].iov_base + nwritten;
+               wc->iov[0].iov_len -= nwritten;
                break;
            }
+           nwritten -= wc->iov[0].iov_len;
+           wc->iov++;
+           wc->iovcnt--;
        }
        break;
     }