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usb: limit combined packets to 1 MiB (CVE-2021-3527)

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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>
This commit is contained in:
Gerd Hoffmann 2021-05-03 15:29:15 +02:00
parent 06aa50c06c
commit 05a40b172e
1 changed files with 3 additions and 1 deletions
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4
hw/usb/combined-packet.c
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@ -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) {