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[Qemu-devel] [PATCH 1/4] ui: avoid risk of 32-bit int overflow in VNC bu
From: |
Daniel P . Berrangé |
Subject: |
[Qemu-devel] [PATCH 1/4] ui: avoid risk of 32-bit int overflow in VNC buffer check |
Date: |
Mon, 5 Feb 2018 11:49:35 +0000 |
For very large framebuffers, it is theoretically possible for the result
of 'vs->throttle_output_offset * VNC_THROTTLE_OUTPUT_LIMIT_SCALE' to
exceed the size of a 32-bit int. For this to happen in practice, the
video RAM would have to be set to a large enough value, which is not
likely today. None the less we can be paranoid against future growth by
using division instead of multiplication when checking the limits.
Reported-by: Laszlo Ersek <address@hidden>
Signed-off-by: Daniel P. Berrangé <address@hidden>
---
ui/vnc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/ui/vnc.c b/ui/vnc.c
index 93731accb6..e14e524764 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -1572,8 +1572,8 @@ void vnc_write(VncState *vs, const void *data, size_t len)
* handshake, or from the job thread's VncState clone
*/
if (vs->throttle_output_offset != 0 &&
- vs->output.offset > (vs->throttle_output_offset *
- VNC_THROTTLE_OUTPUT_LIMIT_SCALE)) {
+ (vs->output.offset / VNC_THROTTLE_OUTPUT_LIMIT_SCALE) >
+ vs->throttle_output_offset) {
trace_vnc_client_output_limit(vs, vs->ioc, vs->output.offset,
vs->throttle_output_offset);
vnc_disconnect_start(vs);
--
2.14.3