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Commit-Id: 05a40b172e4d691371534828078be47e7fff524c
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 3 May 2021 15:29:15 +0200
Subject: usb: limit combined packets to 1 MiB (CVE-2021-3527)
Bug-Debian: https://bugs.debian.org/988157
usb-host and usb-redirect try to batch bulk transfers by combining many
small usb packets into a single, large transfer request, to reduce the
overhead and improve performance.
This patch adds a size limit of 1 MiB for those combined packets to
restrict the host resources the guest can bind that way.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20210503132915.2335822-6-kraxel@redhat.com>
---
hw/usb/combined-packet.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/hw/usb/combined-packet.c b/hw/usb/combined-packet.c
index 5d57e883dc..e56802f89a 100644
--- a/hw/usb/combined-packet.c
+++ b/hw/usb/combined-packet.c
@@ -171,7 +171,9 @@ void usb_ep_combine_input_packets(USBEndpoint *ep)
if ((p->iov.size % ep->max_packet_size) != 0 || !p->short_not_ok ||
next == NULL ||
/* Work around for Linux usbfs bulk splitting + migration */
- (totalsize == (16 * KiB - 36) && p->int_req)) {
+ (totalsize == (16 * KiB - 36) && p->int_req) ||
+ /* Next package may grow combined package over 1MiB */
+ totalsize > 1 * MiB - ep->max_packet_size) {
usb_device_handle_data(ep->dev, first);
assert(first->status == USB_RET_ASYNC);
if (first->combined) {
--
2.30.2
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