[Qemu-devel] [PATCH] spapr-vty: Fix bad assert() statement

[Thomas Huth]

When using the serial console in the GTK interface of QEMU (and
QEMU has been compiled with CONFIG_VTE), it is possible to trigger
the assert() statement in vty_receive() in spapr_vty.c by pasting
a chunk of text with length > 16 into the QEMU window.
Most of the other serial backends seem to simply drop characters
that they can not handle, so I think we should also do the same in
spapr-vty to fix this issue. And since it is quite ugly when pasted
text is chopped after 16 bytes, we also increase the size of the
input buffer here so that we can at least handle a couple of text
lines.

Buglink: https://bugs.launchpad.net/qemu/+bug/1639322
Signed-off-by: Thomas Huth <address@hidden>
---
 hw/char/spapr_vty.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/hw/char/spapr_vty.c b/hw/char/spapr_vty.c
index 31822fe..bee6c34 100644
--- a/hw/char/spapr_vty.c
+++ b/hw/char/spapr_vty.c
@@ -1,4 +1,5 @@
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "qemu-common.h"
 #include "cpu.h"
@@ -7,7 +8,7 @@
 #include "hw/ppc/spapr.h"
 #include "hw/ppc/spapr_vio.h"
 
-#define VTERM_BUFSIZE   16
+#define VTERM_BUFSIZE   2048
 
 typedef struct VIOsPAPRVTYDevice {
     VIOsPAPRDevice sdev;
@@ -37,7 +38,15 @@ static void vty_receive(void *opaque, const uint8_t *buf, 
int size)
         qemu_irq_pulse(spapr_vio_qirq(&dev->sdev));
     }
     for (i = 0; i < size; i++) {
-        assert((dev->in - dev->out) < VTERM_BUFSIZE);
+        if (dev->in - dev->out >= VTERM_BUFSIZE) {
+            static bool reported;
+            if (!reported) {
+                error_report("VTY input buffer exhausted - characters dropped."
+                             " (input size = %i)", size);
+                reported = true;
+            }
+            break;
+        }
         dev->buf[dev->in++ % VTERM_BUFSIZE] = buf[i];
     }
 }
-- 
1.8.3.1