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[PATCH] usb: fix setup_len init (CVE-2020-14364)

Gerd Hoffmann posted 1 patch 3 years, 8 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20200825053636.29648-1-kraxel@redhat.com
Maintainers: Gerd Hoffmann <kraxel@redhat.com>
hw/usb/core.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
[PATCH] usb: fix setup_len init (CVE-2020-14364)
Posted by Gerd Hoffmann 3 years, 8 months ago 
Store calculated setup_len in a local variable, verify it, and only
write it to the struct (USBDevice->setup_len) in case it passed the
sanity checks.

This prevents other code (do_token_{in,out} functions specifically)
from working with invalid USBDevice->setup_len values and overrunning
the USBDevice->setup_buf[] buffer.

Fixes: CVE-2020-14364
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Gonglei <arei.gonglei@huawei.com>
---
 hw/usb/core.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/hw/usb/core.c b/hw/usb/core.c
index 5abd128b6bc5..5234dcc73fea 100644
--- a/hw/usb/core.c
+++ b/hw/usb/core.c
@@ -129,6 +129,7 @@ void usb_wakeup(USBEndpoint *ep, unsigned int stream)
 static void do_token_setup(USBDevice *s, USBPacket *p)
 {
     int request, value, index;
+    unsigned int setup_len;
 
     if (p->iov.size != 8) {
         p->status = USB_RET_STALL;
@@ -138,14 +139,15 @@ static void do_token_setup(USBDevice *s, USBPacket *p)
     usb_packet_copy(p, s->setup_buf, p->iov.size);
     s->setup_index = 0;
     p->actual_length = 0;
-    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
-    if (s->setup_len > sizeof(s->data_buf)) {
+    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
+    if (setup_len > sizeof(s->data_buf)) {
         fprintf(stderr,
                 "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
-                s->setup_len, sizeof(s->data_buf));
+                setup_len, sizeof(s->data_buf));
         p->status = USB_RET_STALL;
         return;
     }
+    s->setup_len = setup_len;
 
     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
@@ -259,26 +261,28 @@ static void do_token_out(USBDevice *s, USBPacket *p)
 static void do_parameter(USBDevice *s, USBPacket *p)
 {
     int i, request, value, index;
+    unsigned int setup_len;
 
     for (i = 0; i < 8; i++) {
         s->setup_buf[i] = p->parameter >> (i*8);
     }
 
     s->setup_state = SETUP_STATE_PARAM;
-    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
     s->setup_index = 0;
 
     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
     index   = (s->setup_buf[5] << 8) | s->setup_buf[4];
 
-    if (s->setup_len > sizeof(s->data_buf)) {
+    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
+    if (setup_len > sizeof(s->data_buf)) {
         fprintf(stderr,
                 "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
-                s->setup_len, sizeof(s->data_buf));
+                setup_len, sizeof(s->data_buf));
         p->status = USB_RET_STALL;
         return;
     }
+    s->setup_len = setup_len;
 
     if (p->pid == USB_TOKEN_OUT) {
         usb_packet_copy(p, s->data_buf, s->setup_len);
-- 
2.27.0
Re: [PATCH] usb: fix setup_len init (CVE-2020-14364)
Posted by Li Qiang 3 years, 8 months ago 
Gerd Hoffmann <kraxel@redhat.com> 于2020年8月25日周二 下午1:37写道：
>
> Store calculated setup_len in a local variable, verify it, and only
> write it to the struct (USBDevice->setup_len) in case it passed the
> sanity checks.
>
> This prevents other code (do_token_{in,out} functions specifically)
> from working with invalid USBDevice->setup_len values and overrunning
> the USBDevice->setup_buf[] buffer.
>
> Fixes: CVE-2020-14364
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> Tested-by: Gonglei <arei.gonglei@huawei.com>

Reviewed-by: Li Qiang <liq3ea@gmail.com>

Just see the page.
-->https://access.redhat.com/security/cve/CVE-2020-14364

The 'Attack Vector' of the CVSS score here is 'local'.

Hi Prasad,
I think this should be 'network' as the guest user can touch this in
cloud environment?
What's the consideration here?

Thanks,
Li Qiang

> ---
>  hw/usb/core.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/hw/usb/core.c b/hw/usb/core.c
> index 5abd128b6bc5..5234dcc73fea 100644
> --- a/hw/usb/core.c
> +++ b/hw/usb/core.c
> @@ -129,6 +129,7 @@ void usb_wakeup(USBEndpoint *ep, unsigned int stream)
>  static void do_token_setup(USBDevice *s, USBPacket *p)
>  {
>      int request, value, index;
> +    unsigned int setup_len;
>
>      if (p->iov.size != 8) {
>          p->status = USB_RET_STALL;
> @@ -138,14 +139,15 @@ static void do_token_setup(USBDevice *s, USBPacket *p)
>      usb_packet_copy(p, s->setup_buf, p->iov.size);
>      s->setup_index = 0;
>      p->actual_length = 0;
> -    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
> -    if (s->setup_len > sizeof(s->data_buf)) {
> +    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
> +    if (setup_len > sizeof(s->data_buf)) {
>          fprintf(stderr,
>                  "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
> -                s->setup_len, sizeof(s->data_buf));
> +                setup_len, sizeof(s->data_buf));
>          p->status = USB_RET_STALL;
>          return;
>      }
> +    s->setup_len = setup_len;
>
>      request = (s->setup_buf[0] << 8) | s->setup_buf[1];
>      value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
> @@ -259,26 +261,28 @@ static void do_token_out(USBDevice *s, USBPacket *p)
>  static void do_parameter(USBDevice *s, USBPacket *p)
>  {
>      int i, request, value, index;
> +    unsigned int setup_len;
>
>      for (i = 0; i < 8; i++) {
>          s->setup_buf[i] = p->parameter >> (i*8);
>      }
>
>      s->setup_state = SETUP_STATE_PARAM;
> -    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
>      s->setup_index = 0;
>
>      request = (s->setup_buf[0] << 8) | s->setup_buf[1];
>      value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
>      index   = (s->setup_buf[5] << 8) | s->setup_buf[4];
>
> -    if (s->setup_len > sizeof(s->data_buf)) {
> +    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
> +    if (setup_len > sizeof(s->data_buf)) {
>          fprintf(stderr,
>                  "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
> -                s->setup_len, sizeof(s->data_buf));
> +                setup_len, sizeof(s->data_buf));
>          p->status = USB_RET_STALL;
>          return;
>      }
> +    s->setup_len = setup_len;
>
>      if (p->pid == USB_TOKEN_OUT) {
>          usb_packet_copy(p, s->data_buf, s->setup_len);
> --
> 2.27.0
>
>
Re: [PATCH] usb: fix setup_len init (CVE-2020-14364)
Posted by P J P 3 years, 8 months ago 
  Hello Li,

+-- On Tue, 25 Aug 2020, Li Qiang wrote --+
| Just see the page.
| -->https://access.redhat.com/security/cve/CVE-2020-14364
| 
| The 'Attack Vector' of the CVSS score here is 'local'.
| 
| I think this should be 'network' as the guest user can touch this in cloud 
| environment? What's the consideration here?

  -> https://www.first.org/cvss/v3.1/user-guide#3-5-Scope-Vulnerable-Component-and-Impacted-Component

AV:Network or Adjacent is generally used when issue involves network stack. In 
this case it's a usb device r/w operation.


Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
8685 545E B54C 486B C6EB 271E E285 8B5A F050 DE8D

Patchew 2.1-devel-0870f84

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