Re: [PATCH] net: eepro100: validate various address values

[Li Qiang]

Alexander Bulekov <alxndr@bu.edu> 于2021年2月19日周五 上午9:56写道：
>
> On 210218 1441, Peter Maydell wrote:
> > On Thu, 18 Feb 2021 at 14:13, P J P <ppandit@redhat.com> wrote:
> > >
> > > From: Prasad J Pandit <pjp@fedoraproject.org>
> > >
> > > While processing controller commands, eepro100 emulator gets
> > > command unit(CU) base address OR receive unit (RU) base address
> > > OR command block (CB) address from guest. If these values are not
> > > checked, it may lead to an infinite loop kind of issues. Add checks
> > > to avoid it.


So could you please provide a backtrack?


Thanks,
Li Qiang

> > >
> > > Reported-by: Ruhr-University Bochum <bugs-syssec@rub.de>
> > > Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> > > ---
> > >  hw/net/eepro100.c | 8 +++++++-
> > >  1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c
> > > index 16e95ef9cc..afa1c9b2aa 100644
> > > --- a/hw/net/eepro100.c
> > > +++ b/hw/net/eepro100.c
> > > @@ -843,7 +843,8 @@ static void action_command(EEPRO100State *s)
> > >          bool bit_i;
> > >          bool bit_nc;
> > >          uint16_t ok_status = STATUS_OK;
> > > -        s->cb_address = s->cu_base + s->cu_offset;
> > > +        s->cb_address = s->cu_base + s->cu_offset;  /* uint32_t overflow 
> > > */
> > > +        assert (s->cb_address >= s->cu_base);
> >
> > We get these values from the guest; you can't just assert() on them.
> > You need to do something else.
> >
> > My reading of the 8255x data sheet is that there is nothing
> > in the hardware that forbids the guest from programming the
> > device such that the cu_base + cu_offset wraps around:
> > http://www.intel.com/content/dam/doc/manual/8255x-10-100-mbps-ethernet-controller-software-dev-manual.pdf
> > -- page 30 says that this is all doing 32-bit arithmetic
> > on addresses and doesn't say that there is any special case
> > handling by the device of overflow of that addition.
> >
> > Your commit message isn't very clear about what the failure
> > case is here, but I think the fix has to be something
> > different from this.
>
> Maybe the infinite loop mentioned in the commit message is actually a
> DMA recursion issue? I'm providing a reproducer for a DMA re-entracy
> issue below. With this patch applied, the reproducer triggers the
> assert(), rather than overflowing the stack, so maybe it is the same
> issue?
> -Alex
>
> cat << EOF | ./qemu-system-i386 -display none -machine accel=qtest, -m \
> 512M -device i82559er,netdev=net0 -netdev user,id=net0 -nodefaults \
> -qtest stdio
> outl 0xcf8 0x80001014
> outl 0xcfc 0xc000
> outl 0xcf8 0x80001010
> outl 0xcfc 0xe0020000
> outl 0xcf8 0x80001004
> outw 0xcfc 0x7
> write 0x1ffffc0b 0x1 0x55
> write 0x1ffffc0c 0x1 0xfc
> write 0x1ffffc0d 0x1 0x46
> write 0x1ffffc0e 0x1 0x07
> write 0x746fc59 0x1 0x02
> write 0x746fc5b 0x1 0x02
> write 0x746fc5c 0x1 0xe0
> write 0x4 0x1 0x07
> write 0x5 0x1 0xfc
> write 0x6 0x1 0xff
> write 0x7 0x1 0x1f
> outw 0xc002 0x20
> EOF
>
> Formatted for committing a regression-test:
>
> static void test_fuzz(void)
> {
>     QTestState *s =
>         qtest_init("-display none , -m 512M -device i82559er,netdev=net0 "
>                    "-netdev user,id=net0 -nodefaults");
>     qtest_outl(s, 0xcf8, 0x80001014);
>     qtest_outl(s, 0xcfc, 0xc000);
>     qtest_outl(s, 0xcf8, 0x80001010);
>     qtest_outl(s, 0xcfc, 0xe0020000);
>     qtest_outl(s, 0xcf8, 0x80001004);
>     qtest_outw(s, 0xcfc, 0x7);
>     qtest_bufwrite(s, 0x1ffffc0b, "\x55", 0x1);
>     qtest_bufwrite(s, 0x1ffffc0c, "\xfc", 0x1);
>     qtest_bufwrite(s, 0x1ffffc0d, "\x46", 0x1);
>     qtest_bufwrite(s, 0x1ffffc0e, "\x07", 0x1);
>     qtest_bufwrite(s, 0x746fc59, "\x02", 0x1);
>     qtest_bufwrite(s, 0x746fc5b, "\x02", 0x1);
>     qtest_bufwrite(s, 0x746fc5c, "\xe0", 0x1);
>     qtest_bufwrite(s, 0x4, "\x07", 0x1);
>     qtest_bufwrite(s, 0x5, "\xfc", 0x1);
>     qtest_bufwrite(s, 0x6, "\xff", 0x1);
>     qtest_bufwrite(s, 0x7, "\x1f", 0x1);
>     qtest_outw(s, 0xc002, 0x20);
>     qtest_quit(s);
> }
>
>
> >
> > thanks
> > -- PMM
> >
>