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

[Alexander Bulekov]

On 200911 1520, Alexander Bulekov wrote:
> On 200911 2257, Li Qiang wrote:
> > 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

... and for the stack overflow:

cat << EOF | ./qemu-system-i386 -device pci-ohci,id=usb \
-nodefaults -qtest stdio -nographic
outl 0xcf8 0x80001013
outl 0xcfc 0xfdff5955
outl 0xcf8 0x80001002
outl 0xcfc 0xd3073d2f
writeq 0x55000000 0x5a55b984d3fd0200
clock_step
clock_step
clock_step
clock_step
clock_step
clock_step
write 0x18 0x1 0x7a
write 0x19 0x1 0xab
write 0xab7b 0x1 0xab
write 0xab7f 0x1 0xff
write 0xab82 0x1 0x7a
write 0xab83 0x1 0xab
write 0xab70 0x1 0xff
write 0xab71 0x1 0xff
write 0xab73 0x1 0xff
write 0xab75 0x1 0xab
clock_step
EOF

> > >
> > >      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.
> > 
> 
> Maybe this is the heap-overflow?
> 
> cat << EOF | ./qemu-system-i386 -device pci-ohci,id=usbb \
> -device usb-tablet,bus=usbb.0,port=1,usb_version=1 \
> -nodefaults -qtest stdio -nographic
> outl 0xcf8 0x80001013
> outl 0xcfc 0x1fd555a
> outl 0xcf8 0x80001002
> outl 0xcfc 0x7fe072f
> write 0x5a000004 0x1 0xa5
> write 0x0 0x1 0x26
> write 0x1 0x1 0xfc
> write 0xfc27 0x1 0xaa
> write 0xfc30 0x1 0x04
> write 0x40006 0x1 0x27
> write 0x4000e 0x1 0x27
> write 0x40011 0x1 0xff
> EOF
> 
> ==3325498==ERROR: AddressSanitizer: heap-buffer-overflow 
> WRITE of size 131661824 at 0x6270000031a0 thread T0
> #0 0x5564784a5a9f in __asan_memcpy (u-system-i386+0x2db6a9f)
> #1 0x55647abc4cee in flatview_read_continue exec.c:3246:13
> #2 0x55647abc7513 in flatview_read exec.c:3279:12
> #3 0x55647abc7068 in address_space_read_full exec.c:3292:18
> #4 0x55647abc8208 in address_space_rw exec.c:3320:16
> #5 0x5564798a9467 in dma_memory_rw_relaxed include/sysemu/dma.h:87:18
> #6 0x5564798a8e85 in dma_memory_rw include/sysemu/dma.h:110:12
> #7 0x5564798b1d16 in ohci_copy_iso_td hw/usb/hcd-ohci.c:624:9
> #8 0x5564798a2d66 in ohci_service_iso_td hw/usb/hcd-ohci.c:778:13
> #9 0x556479897e1b in ohci_service_ed_list hw/usb/hcd-ohci.c:1180:21
> #10 0x556479889dc6 in ohci_frame_boundary hw/usb/hcd-ohci.c:1245:9
> #11 0x55647c40c527 in timerlist_run_timers util/qemu-timer.c:572:9
> 
> -Alex
> 
> > 
> > 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
> > >
> > >
> >