[PATCH -fixes v3 0/6] Fixes KASAN and other along the way

Alexandre Ghiti alexandre.ghiti at canonical.com
Thu Mar 10 00:41:57 PST 2022 

Hi,

On Wed, Mar 9, 2022 at 11:52 AM Dmitry Vyukov <dvyukov at google.com> wrote:
>
> On Wed, 9 Mar 2022 at 11:45, Aleksandr Nogikh <nogikh at google.com> wrote:
> >
> > I switched the riscv syzbot instance to KASAN_OUTLINE and now it is
> > finally being fuzzed again!
> >
> > Thank you very much for the series!
>
>
> But all riscv crashes are still classified as "corrupted" and thrown
> away (not reported):
> https://syzkaller.appspot.com/bug?id=d5bc3e0c66d200d72216ab343a67c4327e4a3452
>
> The problem is that risvc oopses don't contain "Call Trace:" in the
> beginning of stack traces, so it's hard to make sense out of them.
> arch/riscv seems to print "Call Trace:" in a wrong function, not where
> all other arches print it.
>

Does the following diff fix this issue?

diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 201ee206fb57..348ca19ccbf8 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -109,12 +109,12 @@ static bool print_trace_address(void *arg,
unsigned long pc)
 noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
                    const char *loglvl)
 {
+       pr_cont("%sCall Trace:\n", loglvl);
        walk_stackframe(task, regs, print_trace_address, (void *)loglvl);
 }

 void show_stack(struct task_struct *task, unsigned long *sp, const
char *loglvl)
 {
-       pr_cont("%sCall Trace:\n", loglvl);
        dump_backtrace(NULL, task, loglvl);
 }

Thanks,

Alex

>
>
> > --
> > Best Regards,
> > Aleksandr
> >
> > On Fri, Mar 4, 2022 at 5:12 AM Palmer Dabbelt <palmer at dabbelt.com> wrote:
> > >
> > > On Tue, 01 Mar 2022 09:39:54 PST (-0800), Palmer Dabbelt wrote:
> > > > On Fri, 25 Feb 2022 07:00:23 PST (-0800), glider at google.com wrote:
> > > >> On Fri, Feb 25, 2022 at 3:47 PM Alexandre Ghiti <
> > > >> alexandre.ghiti at canonical.com> wrote:
> > > >>
> > > >>> On Fri, Feb 25, 2022 at 3:31 PM Alexander Potapenko <glider at google.com>
> > > >>> wrote:
> > > >>> >
> > > >>> >
> > > >>> >
> > > >>> > On Fri, Feb 25, 2022 at 3:15 PM Alexandre Ghiti <
> > > >>> alexandre.ghiti at canonical.com> wrote:
> > > >>> >>
> > > >>> >> On Fri, Feb 25, 2022 at 3:10 PM Alexander Potapenko <glider at google.com>
> > > >>> wrote:
> > > >>> >> >
> > > >>> >> >
> > > >>> >> >
> > > >>> >> > On Fri, Feb 25, 2022 at 3:04 PM Alexandre Ghiti <
> > > >>> alexandre.ghiti at canonical.com> wrote:
> > > >>> >> >>
> > > >>> >> >> On Fri, Feb 25, 2022 at 2:06 PM Marco Elver <elver at google.com>
> > > >>> wrote:
> > > >>> >> >> >
> > > >>> >> >> > On Fri, 25 Feb 2022 at 13:40, Alexandre Ghiti
> > > >>> >> >> > <alexandre.ghiti at canonical.com> wrote:
> > > >>> >> >> > >
> > > >>> >> >> > > As reported by Aleksandr, syzbot riscv is broken since commit
> > > >>> >> >> > > 54c5639d8f50 ("riscv: Fix asan-stack clang build"). This commit
> > > >>> actually
> > > >>> >> >> > > breaks KASAN_INLINE which is not fixed in this series, that will
> > > >>> come later
> > > >>> >> >> > > when found.
> > > >>> >> >> > >
> > > >>> >> >> > > Nevertheless, this series fixes small things that made the syzbot
> > > >>> >> >> > > configuration + KASAN_OUTLINE fail to boot.
> > > >>> >> >> > >
> > > >>> >> >> > > Note that even though the config at [1] boots fine with this
> > > >>> series, I
> > > >>> >> >> > > was not able to boot the small config at [2] which fails because
> > > >>> >> >> > > kasan_poison receives a really weird address 0x4075706301000000
> > > >>> (maybe a
> > > >>> >> >> > > kasan person could provide some hint about what happens below in
> > > >>> >> >> > > do_ctors -> __asan_register_globals):
> > > >>> >> >> >
> > > >>> >> >> > asan_register_globals is responsible for poisoning redzones around
> > > >>> >> >> > globals. As hinted by 'do_ctors', it calls constructors, and in
> > > >>> this
> > > >>> >> >> > case a compiler-generated constructor that calls
> > > >>> >> >> > __asan_register_globals with metadata generated by the compiler.
> > > >>> That
> > > >>> >> >> > metadata contains information about global variables. Note, these
> > > >>> >> >> > constructors are called on initial boot, but also every time a
> > > >>> kernel
> > > >>> >> >> > module (that has globals) is loaded.
> > > >>> >> >> >
> > > >>> >> >> > It may also be a toolchain issue, but it's hard to say. If you're
> > > >>> >> >> > using GCC to test, try Clang (11 or later), and vice-versa.
> > > >>> >> >>
> > > >>> >> >> I tried 3 different gcc toolchains already, but that did not fix the
> > > >>> >> >> issue. The only thing that worked was setting asan-globals=0 in
> > > >>> >> >> scripts/Makefile.kasan, but ok, that's not a fix.
> > > >>> >> >> I tried to bisect this issue but our kasan implementation has been
> > > >>> >> >> broken quite a few times, so it failed.
> > > >>> >> >>
> > > >>> >> >> I keep digging!
> > > >>> >> >>
> > > >>> >> >
> > > >>> >> > The problem does not reproduce for me with GCC 11.2.0: kernels built
> > > >>> with both [1] and [2] are bootable.
> > > >>> >>
> > > >>> >> Do you mean you reach userspace? Because my image boots too, and fails
> > > >>> >> at some point:
> > > >>> >>
> > > >>> >> [    0.000150] sched_clock: 64 bits at 10MHz, resolution 100ns, wraps
> > > >>> >> every 4398046511100ns
> > > >>> >> [    0.015847] Console: colour dummy device 80x25
> > > >>> >> [    0.016899] printk: console [tty0] enabled
> > > >>> >> [    0.020326] printk: bootconsole [ns16550a0] disabled
> > > >>> >>
> > > >>> >
> > > >>> > In my case, QEMU successfully boots to the login prompt.
> > > >>> > I am running QEMU 6.2.0 (Debian 1:6.2+dfsg-2) and an image Aleksandr
> > > >>> shared with me (guess it was built according to this instruction:
> > > >>> https://github.com/google/syzkaller/blob/master/docs/linux/setup_linux-host_qemu-vm_riscv64-kernel.md
> > > >>> )
> > > >>> >
> > > >>>
> > > >>> Nice thanks guys! I always use the latest opensbi and not the one that
> > > >>> is embedded in qemu, which is the only difference between your command
> > > >>> line (which works) and mine (which does not work). So the issue is
> > > >>> probably there, I really need to investigate that now.
> > > >>>
> > > >>> Great to hear that!
> > > >>
> > > >>
> > > >>> That means I only need to fix KASAN_INLINE and we're good.
> > > >>>
> > > >>> I imagine Palmer can add your Tested-by on the series then?
> > > >>>
> > > >> Sure :)
> > > >
> > > > Do you mind actually posting that (i, the Tested-by tag)?  It's less
> > > > likely to get lost that way.  I intend on taking this into fixes ASAP,
> > > > my builds have blown up for some reason (I got bounced between machines,
> > > > so I'm blaming that) so I need to fix that first.
> > >
> > > This is on fixes (with a "Tested-by: Alexander Potapenko
> > > <glider at google.com>"), along with some trivial commit message fixes.
> > >
> > > Thanks!
> > >
> > > >
> > > >>
> > > >>>
> > > >>> Thanks again!
> > > >>>
> > > >>> Alex
> > > >>>
> > > >>> >>
> > > >>> >> It traps here.
> > > >>> >>
> > > >>> >> > FWIW here is how I run them:
> > > >>> >> >
> > > >>> >> > qemu-system-riscv64 -m 2048 -smp 1 -nographic -no-reboot \
> > > >>> >> >   -device virtio-rng-pci -machine virt -device \
> > > >>> >> >   virtio-net-pci,netdev=net0 -netdev \
> > > >>> >> >   user,id=net0,restrict=on,hostfwd=tcp:127.0.0.1:12529-:22 -device \
> > > >>> >> >   virtio-blk-device,drive=hd0 -drive \
> > > >>> >> >   file=${IMAGE},if=none,format=raw,id=hd0 -snapshot \
> > > >>> >> >   -kernel ${KERNEL_SRC_DIR}/arch/riscv/boot/Image -append
> > > >>> "root=/dev/vda
> > > >>> >> >   console=ttyS0 earlyprintk=serial"
> > > >>> >> >
> > > >>> >> >
> > > >>> >> >>
> > > >>> >> >> Thanks for the tips,
> > > >>> >> >>
> > > >>> >> >> Alex
> > > >>> >> >
> > > >>> >> >
> > > >>> >> >
> > > >>> >> > --
> > > >>> >> > Alexander Potapenko
> > > >>> >> > Software Engineer
> > > >>> >> >
> > > >>> >> > Google Germany GmbH
> > > >>> >> > Erika-Mann-Straße, 33
> > > >>> >> > 80636 München
> > > >>> >> >
> > > >>> >> > Geschäftsführer: Paul Manicle, Liana Sebastian
> > > >>> >> > Registergericht und -nummer: Hamburg, HRB 86891
> > > >>> >> > Sitz der Gesellschaft: Hamburg
> > > >>> >> >
> > > >>> >> > Diese E-Mail ist vertraulich. Falls Sie diese fälschlicherweise
> > > >>> erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes
> > > >>> weiter, löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte
> > > >>> wissen, dass die E-Mail an die falsche Person gesendet wurde.
> > > >>> >> >
> > > >>> >> >
> > > >>> >> >
> > > >>> >> > This e-mail is confidential. If you received this communication by
> > > >>> mistake, please don't forward it to anyone else, please erase all copies
> > > >>> and attachments, and please let me know that it has gone to the wrong
> > > >>> person.
> > > >>> >>
> > > >>> >> --
> > > >>> >> You received this message because you are subscribed to the Google
> > > >>> Groups "kasan-dev" group.
> > > >>> >> To unsubscribe from this group and stop receiving emails from it, send
> > > >>> an email to kasan-dev+unsubscribe at googlegroups.com.
> > > >>> >> To view this discussion on the web visit
> > > >>> https://groups.google.com/d/msgid/kasan-dev/CA%2BzEjCsQPVYSV7CdhKnvjujXkMXuRQd%3DVPok1awb20xifYmidw%40mail.gmail.com
> > > >>> .
> > > >>> >
> > > >>> >
> > > >>> >
> > > >>> > --
> > > >>> > Alexander Potapenko
> > > >>> > Software Engineer
> > > >>> >
> > > >>> > Google Germany GmbH
> > > >>> > Erika-Mann-Straße, 33
> > > >>> > 80636 München
> > > >>> >
> > > >>> > Geschäftsführer: Paul Manicle, Liana Sebastian
> > > >>> > Registergericht und -nummer: Hamburg, HRB 86891
> > > >>> > Sitz der Gesellschaft: Hamburg
> > > >>> >
> > > >>> > Diese E-Mail ist vertraulich. Falls Sie diese fälschlicherweise erhalten
> > > >>> haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter,
> > > >>> löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte wissen,
> > > >>> dass die E-Mail an die falsche Person gesendet wurde.
> > > >>> >
> > > >>> >
> > > >>> >
> > > >>> > This e-mail is confidential. If you received this communication by
> > > >>> mistake, please don't forward it to anyone else, please erase all copies
> > > >>> and attachments, and please let me know that it has gone to the wrong
> > > >>> person.
> > > >>>
> > > >>> --
> > > >>> You received this message because you are subscribed to the Google Groups
> > > >>> "kasan-dev" group.
> > > >>> To unsubscribe from this group and stop receiving emails from it, send an
> > > >>> email to kasan-dev+unsubscribe at googlegroups.com.
> > > >>> To view this discussion on the web visit
> > > >>> https://groups.google.com/d/msgid/kasan-dev/CA%2BzEjCuJw8N0dUmQNdFqDM96bzKqPDjRe4FUnOCbjhJtO0R8Hg%40mail.gmail.com
> > > >>> .
> > > >>>
> > > >>
> > > >>
> > > >> --
> > > >> Alexander Potapenko
> > > >> Software Engineer
> > > >>
> > > >> Google Germany GmbH
> > > >> Erika-Mann-Straße, 33
> > > >> 80636 München
> > > >>
> > > >> Geschäftsführer: Paul Manicle, Liana Sebastian
> > > >> Registergericht und -nummer: Hamburg, HRB 86891
> > > >> Sitz der Gesellschaft: Hamburg
> > > >>
> > > >> Diese E-Mail ist vertraulich. Falls Sie diese fälschlicherweise erhalten
> > > >> haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter,
> > > >> löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte wissen,
> > > >> dass die E-Mail an die falsche Person gesendet wurde.
> > > >>
> > > >>
> > > >>
> > > >> This e-mail is confidential. If you received this communication by mistake,
> > > >> please don't forward it to anyone else, please erase all copies and
> > > >> attachments, and please let me know that it has gone to the wrong person.

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