45 lines
1.7 KiB
Diff
45 lines
1.7 KiB
Diff
|
From ad0343a9c903b79c6dd3ecdafb05a704c14514b9 Mon Sep 17 00:00:00 2001
|
||
|
|
From: Hans de Goede <hdegoede@redhat.com>
|
||
|
|
Date: Fri, 5 Apr 2013 11:30:24 +0200
|
||
|
|
Subject: [PATCH] spice-qemu-char: vmc_write: Don't write more bytes then we're
|
||
|
|
asked too
|
||
|
|
|
||
|
|
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 <hdegoede@redhat.com>
|
||
|
|
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
|
||
|
|
(cherry picked from commit 75c439bc65c07d76f5e74c734ed5432bc6114a3b)
|
||
|
|
---
|
||
|
|
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 5065240..82f3f77 100644
|
||
|
|
--- a/spice-qemu-char.c
|
||
|
|
+++ b/spice-qemu-char.c
|
||
|
|
@@ -41,7 +41,8 @@ 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;
|
||
|
|
}
|