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[Qemu-devel] [PATCH, RESEND] Fix SIGFPE race for vnc display resize
From: |
Chris Webb |
Subject: |
[Qemu-devel] [PATCH, RESEND] Fix SIGFPE race for vnc display resize |
Date: |
Thu, 26 Aug 2010 12:43:55 +0100 |
User-agent: |
Mutt/1.5.20 (2009-06-14) |
cc39a92cbfc8 fixed a SIGFPE where the screen is resized to width/hight 1 and
then receives a mouse click. However, there is a still a tiny window here for
a race between the test for width/height > 1 and the division.
Signed-off-by: Chris Webb <address@hidden>
---
Sending this as I've just seen a SIGFPE from one of the qemu-kvm VMs running
in our public-facing cluster. Running gdb on the resulting core dump pointed
at line #1424 of vnc.c:
1423 if (vs->absolute) {
1424 kbd_mouse_event(ds_get_width(vs->ds) > 1 ?
1425 x * 0x7FFF / (ds_get_width(vs->ds) - 1) :
0x4000,
1426 ds_get_height(vs->ds) > 1 ?
1427 y * 0x7FFF / (ds_get_height(vs->ds) - 1) :
0x4000,
1428 dz, buttons);
I think this must have been a (tight) race between the comparison and the
division. This should probably go to the 0.12-stable branch too as that's
where I saw the crash. I can send a rebased patch if that's more convenient?
A pity this crash happened just after the release of 0.12.5 rather than a
week or two earlier!
ui/vnc.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/ui/vnc.c b/ui/vnc.c
index 7fc40ac..e04ebdf 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -1410,10 +1410,10 @@ static void pointer_event(VncState *vs, int button_mask,
dz = 1;
if (vs->absolute) {
- kbd_mouse_event(ds_get_width(vs->ds) > 1 ?
- x * 0x7FFF / (ds_get_width(vs->ds) - 1) : 0x4000,
- ds_get_height(vs->ds) > 1 ?
- y * 0x7FFF / (ds_get_height(vs->ds) - 1) : 0x4000,
+ int width = ds_get_width(vs->ds);
+ int height = ds_get_height(vs->ds);
+ kbd_mouse_event(width > 1 ? x * 0x7FFF / (width - 1) : 0x4000,
+ height > 1 ? y * 0x7FFF / (height - 1) : 0x4000,
dz, buttons);
} else if (vnc_has_feature(vs, VNC_FEATURE_POINTER_TYPE_CHANGE)) {
x -= 0x7FFF;
--
1.7.1.1
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