Re: [PATCH] hw: usb: hcd-ohci: check len and frame_number variables

[Li Qiang <liq3ea@gmail.com>]

P J P <ppandit@redhat.com> 于2020年9月11日周五 下午8:30写道：
>
> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> While servicing the OHCI transfer descriptors(TD), OHCI host
> controller derives variables 'start_addr', 'end_addr', 'len'
> etc. from values supplied by the host controller driver.
> Host controller driver may supply values such that using
> above variables leads to out-of-bounds access or loop issues.
> Add checks to avoid them.
>
> AddressSanitizer: stack-buffer-overflow on address 0x7ffd53af76a0
>   READ of size 2 at 0x7ffd53af76a0 thread T0
>   #0 ohci_service_iso_td ../hw/usb/hcd-ohci.c:734
>   #1 ohci_service_ed_list ../hw/usb/hcd-ohci.c:1180
>   #2 ohci_process_lists ../hw/usb/hcd-ohci.c:1214
>   #3 ohci_frame_boundary ../hw/usb/hcd-ohci.c:1257
>   #4 timerlist_run_timers ../util/qemu-timer.c:572
>   #5 qemu_clock_run_timers ../util/qemu-timer.c:586
>   #6 qemu_clock_run_all_timers ../util/qemu-timer.c:672
>   #7 main_loop_wait ../util/main-loop.c:527
>   #8 qemu_main_loop ../softmmu/vl.c:1676
>   #9 main ../softmmu/main.c:50
>

Hello Prasad,
Could you also provide the reproducer?

> Reported-by: Gaoning Pan <pgn@zju.edu.cn>
> Reported-by: Yongkang Jia <j_kangel@163.com>
> Reported-by: Yi Ren <yunye.ry@alibaba-inc.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/usb/hcd-ohci.c | 29 +++++++++++++++++++++++++++--
>  1 file changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
> index 1e6e85e86a..76fb9282e3 100644
> --- a/hw/usb/hcd-ohci.c
> +++ b/hw/usb/hcd-ohci.c
> @@ -691,6 +691,11 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed,
>             the next ISO TD of the same ED */
>          trace_usb_ohci_iso_td_relative_frame_number_big(relative_frame_number,
>                                                          frame_count);
> +        if (OHCI_CC_DATAOVERRUN == OHCI_BM(iso_td.flags, TD_CC)) {
> +            /* avoid infinite loop */
> +            return 1;
> +        }

I think it is better to split this patch to 2 or three as the infinite
loop as the buffer overflow are independent.

1. here the infinite loop

> +
>          OHCI_SET_BM(iso_td.flags, TD_CC, OHCI_CC_DATAOVERRUN);
>          ed->head &= ~OHCI_DPTR_MASK;
>          ed->head |= (iso_td.next & OHCI_DPTR_MASK);
> @@ -731,7 +736,11 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed,
>      }
>
>      start_offset = iso_td.offset[relative_frame_number];
> -    next_offset = iso_td.offset[relative_frame_number + 1];
> +    if (relative_frame_number < frame_count) {
> +        next_offset = iso_td.offset[relative_frame_number + 1];
> +    } else {
> +        next_offset = iso_td.be;
> +    }

2. here the stack buffer overflow

>
>      if (!(OHCI_BM(start_offset, TD_PSW_CC) & 0xe) ||
>          ((relative_frame_number < frame_count) &&
> @@ -764,7 +773,12 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed,
>          }
>      } else {
>          /* Last packet in the ISO TD */
> -        end_addr = iso_td.be;
> +        end_addr = next_offset;
> +    }
> +
> +    if (start_addr > end_addr) {
> +        trace_usb_ohci_iso_td_bad_cc_overrun(start_addr, end_addr);
> +        return 1;
>      }
>
>      if ((start_addr & OHCI_PAGE_MASK) != (end_addr & OHCI_PAGE_MASK)) {
> @@ -773,6 +787,9 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed,
>      } else {
>          len = end_addr - start_addr + 1;
>      }
> +    if (len > sizeof(ohci->usb_buf)) {
> +        len = sizeof(ohci->usb_buf);
> +    }
>
>      if (len && dir != OHCI_TD_DIR_IN) {
>          if (ohci_copy_iso_td(ohci, start_addr, end_addr, ohci->usb_buf, len,
> @@ -975,8 +992,16 @@ static int ohci_service_td(OHCIState *ohci, struct ohci_ed *ed)
>          if ((td.cbp & 0xfffff000) != (td.be & 0xfffff000)) {
>              len = (td.be & 0xfff) + 0x1001 - (td.cbp & 0xfff);
>          } else {
> +            if (td.cbp > td.be) {
> +                trace_usb_ohci_iso_td_bad_cc_overrun(td.cbp, td.be);
> +                ohci_die(ohci);
> +                return 1;
> +            }
>              len = (td.be - td.cbp) + 1;
>          }
> +        if (len > sizeof(ohci->usb_buf)) {
> +            len = sizeof(ohci->usb_buf);
> +        }
>

3. Then here is the heap overflow.


So I think it can be more easier to review to split this to 3 patches.

Thanks,
Li Qiang

>          pktlen = len;
>          if (len && dir != OHCI_TD_DIR_IN) {
> --
> 2.26.2
>
>