Re: [PATCH-for-6.2 v3 2/2] tests/qtest/fdc-test: Add a regression test for CVE-2021-20196

[Hanna Reitz]

On 24.11.21 13:50, Philippe Mathieu-Daudé wrote:
> On 11/23/21 15:14, Hanna Reitz wrote:
> > On 23.11.21 14:49, Philippe Mathieu-Daudé wrote:
> > > On 11/23/21 14:42, Hanna Reitz wrote:
> > > > On 18.11.21 13:06, Philippe Mathieu-Daudé wrote:
> > > > > From: Alexander Bulekov <alxndr@bu.edu>
> > > > >
> > > > > Without the previous commit, when running 'make check-qtest-i386'
> > > > > with QEMU configured with '--enable-sanitizers' we get:
> > > > >
> > > > >      AddressSanitizer:DEADLYSIGNAL
> > > > >      =================================================================
> > > > >      ==287878==ERROR: AddressSanitizer: SEGV on unknown address
> > > > > 0x000000000344
> > > > >      ==287878==The signal is caused by a WRITE memory access.
> > > > >      ==287878==Hint: address points to the zero page.
> > > > >          #0 0x564b2e5bac27 in blk_inc_in_flight
> > > > > block/block-backend.c:1346:5
> > > > >          #1 0x564b2e5bb228 in blk_pwritev_part
> > > > > block/block-backend.c:1317:5
> > > > >          #2 0x564b2e5bcd57 in blk_pwrite block/block-backend.c:1498:11
> > > > >          #3 0x564b2ca1cdd3 in fdctrl_write_data hw/block/fdc.c:2221:17
> > > > >          #4 0x564b2ca1b2f7 in fdctrl_write hw/block/fdc.c:829:9
> > > > >          #5 0x564b2dc49503 in portio_write softmmu/ioport.c:201:9
> > > > >
> > > > > Add the reproducer for CVE-2021-20196.
> > > > >
> > > > > Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
> > > > > Message-Id: <20210319050906.14875-2-alxndr@bu.edu>
> > > > > [PMD: Rebased, use global test_image]
> > > > > Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
> > > > > Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> > > > > ---
> > > > >     tests/qtest/fdc-test.c | 21 +++++++++++++++++++++
> > > > >     1 file changed, 21 insertions(+)
> > > > Not sure if I’m doing something wrong, but:
> > > >
> > > > Using the global test_image brings a problem, namely that this test
> > > > fails unconditionally (for me at least...?), with the reason being that
> > > > the global QEMU instance (launched by qtest_start(), quit by
> > > > qtest_end()) still has that image open, so by launching a second
> > > > instance concurrently, I get this:
> > > >
> > > > qemu-system-x86_64: Failed to get "write" lock
> > > > Is another process using the image [/tmp/qtest.xV4IxX]?
> > > Hmm I had too many odd problems running qtests in parallel so I
> > > switched to 'make check-qtest -j1' more than 1 year ago, which
> > > is probably why I haven't noticed that issue.
> > I’ve run the test with
> >
> > QTEST_QEMU_BINARY=$PWD/qemu-system-x86_64 tests/qtest/fdc-test
> >
> > so there definitely weren’t any other tests running at the same time.  I
> > don’t know why you don’t encounter this problem, but it’s caused by the
> > concurrent QEMU instance launched in the very same test (qtest_start()
> > in main(), and cleaned up by qtest_end() after g_test_run()).
> I run all my qtests on top of this patch, otherwise I can't
> get any coredump:
> https://lore.kernel.org/qemu-devel/20200707031920.17428-1-f4bug@amsat.org/
> But I don't think it mattered here...

I can give that a try, but since I use coredumpctl, I generally don’t 
have a problem with one coredump overwriting another (only that I need 
to give a PID to `coredumpctl gdb` to load not the latest coredump (the 
qtest) but the one before (qemu)).

Hm, perhaps the problem is that I never applied the other series before 
this one.  Also one thing that remains to be tested...

Hanna