From: Hans de Goede <hdego...@redhat.com>
This one took me eons to debug, but I've finally found it now, oh well.
The usage of the MIN macro in this line:
last_out = MIN(len, qemu_chr_be_can_write(scd->chr));
Causes qemu_chr_be_can_write to be called *twice*, since the MIN macro
evaluates its arguments twice (bad MIN macro, bad!). And the result of
the call can change between the 2 calls since the guest may have consumed
some data from the virtio ringbuffer between the calls!
When this happens it is possible for qemu_chr_be_can_write to return less
then len in the call made for the comparision, and then to return more then
len in the actual call for the return-value of MIN, after which we will end
up writing len data + some extra garbage, not good.
This patch fixes this by only calling qemu_chr_be_can_write once.
Signed-off-by: Hans de Goede <hdego...@redhat.com>
Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
spice-qemu-char.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/spice-qemu-char.c b/spice-qemu-char.c
index ff95fcb..f10970c 100644
--- a/spice-qemu-char.c
+++ b/spice-qemu-char.c
@@ -35,7 +35,8 @@ static int vmc_write(SpiceCharDeviceInstance *sin, const
uint8_t *buf, int len)
uint8_t* p = (uint8_t*)buf;
while (len > 0) {
- last_out = MIN(len, qemu_chr_be_can_write(scd->chr));
+ int can_write = qemu_chr_be_can_write(scd->chr);
+ last_out = MIN(len, can_write);
if (last_out <= 0) {
break;
}
--
1.7.9.7
