chardev: fix pty_chr_timer

pty_chr_timer first calls pty_chr_update_read_handler(), then clears
timer_tag (because it is a one-shot timer).   This is the wrong order
though.  pty_chr_update_read_handler might re-arm time timer, and the
new timer_tag gets overwitten in that case.

This leads to crashes when unplugging a pty chardev:  pty_chr_close
thinks no timer is running -> timer isn't canceled -> pty_chr_timer gets
called with stale CharDevState -> BOOM.

This patch fixes the ordering.
Kill the pointless goto while being at it.

https://bugzilla.redhat.com/show_bug.cgi?id=994414

Cc: qemu-stable@nongnu.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit b0d768c35e08d2057b63e8e77e7a513c447199fa)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/qemu-char.c b/qemu-char.c
index 1be1cf676eef7dbf2ec41d10e76d2ab255023d2f..1621fbd30f40b128ceecbe11c39814b0ec832ddd 100644 (file)
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -1026,15 +1026,11 @@ static gboolean pty_chr_timer(gpointer opaque)
     struct CharDriverState *chr = opaque;
     PtyCharDriver *s = chr->opaque;
 
-    if (s->connected) {
-        goto out;
-    }
-
-    /* Next poll ... */
-    pty_chr_update_read_handler(chr);
-
-out:
     s->timer_tag = 0;
+    if (!s->connected) {
+        /* Next poll ... */
+        pty_chr_update_read_handler(chr);
+    }
     return FALSE;
 }