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From feb16ff29a13a4286389bb8b9d4f541aab9b84f1 Mon Sep 17 00:00:00 2001
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From: Jon Maloy <jmaloy@redhat.com>
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Date: Thu, 3 Sep 2020 15:27:13 -0400
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Subject: [PATCH] usb: fix setup_len init (CVE-2020-14364)
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RH-Author: Jon Maloy <jmaloy@redhat.com>
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Message-id: <20200903152713.1420531-2-jmaloy@redhat.com>
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Patchwork-id: 98271
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O-Subject: [RHEL-8.3.0 qemu-kvm PATCH 1/1] usb: fix setup_len init (CVE-2020-14364)
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Bugzilla: 1869710
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Gerd Hoffmann <kraxel@redhat.com>
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From: Gerd Hoffmann <kraxel@redhat.com>
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Store calculated setup_len in a local variable, verify it, and only
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write it to the struct (USBDevice->setup_len) in case it passed the
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sanity checks.
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This prevents other code (do_token_{in,out} functions specifically)
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from working with invalid USBDevice->setup_len values and overrunning
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the USBDevice->setup_buf[] buffer.
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Fixes: CVE-2020-14364
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Tested-by: Gonglei <arei.gonglei@huawei.com>
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Reviewed-by: Li Qiang <liq3ea@gmail.com>
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Message-id: 20200825053636.29648-1-kraxel@redhat.com
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(cherry picked from commit b946434f2659a182afc17e155be6791ebfb302eb)
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Signed-off-by: Jon Maloy <jmaloy@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 hw/usb/core.c | 16 ++++++++++------
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 1 file changed, 10 insertions(+), 6 deletions(-)
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diff --git a/hw/usb/core.c b/hw/usb/core.c
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index 5abd128b6b..5234dcc73f 100644
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--- a/hw/usb/core.c
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+++ b/hw/usb/core.c
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@@ -129,6 +129,7 @@ void usb_wakeup(USBEndpoint *ep, unsigned int stream)
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 static void do_token_setup(USBDevice *s, USBPacket *p)
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 {
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     int request, value, index;
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+    unsigned int setup_len;
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     if (p->iov.size != 8) {
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         p->status = USB_RET_STALL;
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@@ -138,14 +139,15 @@ static void do_token_setup(USBDevice *s, USBPacket *p)
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     usb_packet_copy(p, s->setup_buf, p->iov.size);
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     s->setup_index = 0;
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     p->actual_length = 0;
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-    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
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-    if (s->setup_len > sizeof(s->data_buf)) {
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+    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
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+    if (setup_len > sizeof(s->data_buf)) {
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         fprintf(stderr,
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                 "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
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-                s->setup_len, sizeof(s->data_buf));
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+                setup_len, sizeof(s->data_buf));
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         p->status = USB_RET_STALL;
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         return;
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     }
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+    s->setup_len = setup_len;
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     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
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     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
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@@ -259,26 +261,28 @@ static void do_token_out(USBDevice *s, USBPacket *p)
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 static void do_parameter(USBDevice *s, USBPacket *p)
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 {
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     int i, request, value, index;
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+    unsigned int setup_len;
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     for (i = 0; i < 8; i++) {
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         s->setup_buf[i] = p->parameter >> (i*8);
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     }
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     s->setup_state = SETUP_STATE_PARAM;
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-    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
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     s->setup_index = 0;
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     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
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     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
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     index   = (s->setup_buf[5] << 8) | s->setup_buf[4];
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-    if (s->setup_len > sizeof(s->data_buf)) {
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+    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
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+    if (setup_len > sizeof(s->data_buf)) {
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         fprintf(stderr,
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                 "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
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-                s->setup_len, sizeof(s->data_buf));
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+                setup_len, sizeof(s->data_buf));
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         p->status = USB_RET_STALL;
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         return;
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     }
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+    s->setup_len = setup_len;
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     if (p->pid == USB_TOKEN_OUT) {
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         usb_packet_copy(p, s->data_buf, s->setup_len);
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-- 
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2.27.0
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