[Qemu-devel] Re: [FOR 0.12][PATCH] monitor: Accept input only byte-wise

[Paolo Bonzini]

The QEMU code appears to be written to assume that it will recvmsg() a
complete monitor command in one go + process that, because it closes the
FD the moment the data from any recvmsg() is dealt with.

This is buggy anyway.  This should fix it too:

diff --git a/monitor.c b/monitor.c
index 5659991..225a922 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2408,15 +2408,6 @@
         return -1;
     }

-    fd = dup(fd);
-    if (fd == -1) {
-        if (errno == EMFILE)
-            qerror_report(QERR_TOO_MANY_FILES);
-        else
-            qerror_report(QERR_UNDEFINED_ERROR);
-        return -1;
-    }
-
     QLIST_FOREACH(monfd, &mon->fds, next) {
         if (strcmp(monfd->name, fdname) != 0) {
             continue;
diff --git a/qemu-char.c b/qemu-char.c
index 05df971..ac65a1c 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2000,8 +2000,9 @@
 static int tcp_get_msgfd(CharDriverState *chr)
 {
     TCPCharDriver *s = chr->opaque;
-
-    return s->msgfd;
+    int fd = s->msgfd;
+    s->msgfd = -1;
+    return fd;
 }

 #ifndef _WIN32
@@ -2089,10 +2090,6 @@ static void tcp_chr_read(void *opaque)
             tcp_chr_process_IAC_bytes(chr, s, buf, &size);
         if (size > 0)
             qemu_chr_read(chr, buf, size);
-        if (s->msgfd != -1) {
-            close(s->msgfd);
-            s->msgfd = -1;
-        }
     }
 }


Paolo