Messages in this thread | | | Date | Mon, 16 May 2022 14:05:53 +0200 | Subject | Re: [syzbot] riscv/fixes boot error: can't ssh into the instance | From | Alexandre Ghiti <> |
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On 5/12/22 13:48, Dmitry Vyukov wrote: > On Fri, 18 Feb 2022 at 14:45, Alexandre Ghiti > <alexandre.ghiti@canonical.com> wrote: >> Hi Aleksandr, >> >> On Thu, Feb 17, 2022 at 6:08 PM Aleksandr Nogikh <nogikh@google.com> wrote: >>> Hi Alex, >>> >>> On Thu, Feb 17, 2022 at 5:53 PM Alexandre Ghiti >>> <alexandre.ghiti@canonical.com> wrote: >>>> Aleksandr, >>>> >>>> On Wed, Feb 16, 2022 at 5:58 PM Alexandre Ghiti >>>> <alexandre.ghiti@canonical.com> wrote: >>>>> First, thank you for working on this. >>>>> >>>>> On Wed, Feb 16, 2022 at 5:17 PM Aleksandr Nogikh <nogikh@google.com> wrote: >>>>>> If I use just defconfig + DEBUG_VIRTUAL, without any KASAN, it begins >>>>>> to boot, but overwhelms me with tons of `virt_to_phys used for >>>>>> non-linear address:` errors. >>>>>> >>>>>> Like that >>>>>> >>>>>> [ 2.701271] virt_to_phys used for non-linear address: >>>>>> 00000000b59e31b6 (0xffffffff806c2000) >>>>>> [ 2.701727] WARNING: CPU: 0 PID: 1 at arch/riscv/mm/physaddr.c:16 >>>>>> __virt_to_phys+0x7e/0x86 >>>>>> [ 2.702207] Modules linked in: >>>>>> [ 2.702393] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W >>>>>> 5.17.0-rc1 #1 >>>>>> [ 2.702806] Hardware name: riscv-virtio,qemu (DT) >>>>>> [ 2.703051] epc : __virt_to_phys+0x7e/0x86 >>>>>> [ 2.703298] ra : __virt_to_phys+0x7e/0x86 >>>>>> [ 2.703547] epc : ffffffff80008448 ra : ffffffff80008448 sp : >>>>>> ffff8f800021bde0 >>>>>> [ 2.703977] gp : ffffffff80ed9b30 tp : ffffaf8001230000 t0 : >>>>>> ffffffff80eea56f >>>>>> [ 2.704704] t1 : ffffffff80eea560 t2 : 0000000000000000 s0 : >>>>>> ffff8f800021be00 >>>>>> [ 2.705153] s1 : ffffffff806c2000 a0 : 000000000000004f a1 : >>>>>> ffffffff80e723d8 >>>>>> [ 2.705555] a2 : 0000000000000010 a3 : fffffffffffffffe a4 : >>>>>> 0000000000000000 >>>>>> [ 2.706027] a5 : 0000000000000000 a6 : 0000000000000005 a7 : >>>>>> ffffffffffffffff >>>>>> [ 2.706474] s2 : ffffffff80b80b08 s3 : 00000000000000c2 s4 : >>>>>> ffffffff806c2000 >>>>>> [ 2.706891] s5 : ffffffff80edba10 s6 : ffffffff80edb960 s7 : >>>>>> 0000000000000001 >>>>>> [ 2.707290] s8 : 00000000000000ff s9 : ffffffff80b80b40 s10: >>>>>> 00000000000000cc >>>>>> [ 2.707689] s11: ffffaf807e1fcf00 t3 : 0000000000000076 t4 : >>>>>> ffffffffffffffff >>>>>> [ 2.708092] t5 : 00000000000001f2 t6 : ffff8f800021bb48 >>>>>> [ 2.708433] status: 0000000000000120 badaddr: 0000000000000000 >>>>>> cause: 0000000000000003 >>>>>> [ 2.708919] [<ffffffff8011416a>] free_reserved_area+0x72/0x19a >>>>>> [ 2.709296] [<ffffffff80003a5a>] free_initmem+0x6c/0x7c >>>>>> [ 2.709648] [<ffffffff805f60c8>] kernel_init+0x3a/0x10a >>>>>> [ 2.709993] [<ffffffff80002fda>] ret_from_exception+0x0/0xc >>>>>> [ 2.710310] ---[ end trace 0000000000000000 ]--- >>>>>> >>>>> I was able to reproduce this: the first one regarding init_zero_pfn is >>>>> legit but not wrong, I have to check when it was introduced and how to >>>>> fix this. >>>>> Regarding the huge batch that follows, at first sight, I would say >>>>> this is linked to my sv48 patchset but that does not seem important as >>>>> the address is a kernel mapping address so the use of virt_to_phys is >>>>> right. >>>>> >>>>>> On Wed, Feb 16, 2022 at 5:09 PM Aleksandr Nogikh <nogikh@google.com> wrote: >>>>>>> On Wed, Feb 16, 2022 at 12:56 PM Dmitry Vyukov <dvyukov@google.com> wrote: >>>>>>>> On Wed, 16 Feb 2022 at 12:47, Aleksandr Nogikh <nogikh@google.com> wrote: >>>>>>>>> On Wed, Feb 16, 2022 at 11:37 AM Aleksandr Nogikh <nogikh@google.com> wrote: >>>>>>>>>> Hi Alex, >>>>>>>>>> >>>>>>>>>> On Wed, Feb 16, 2022 at 5:14 AM Alexandre Ghiti <alex@ghiti.fr> wrote: >>>>>>>>>>> Hi Dmitry, >>>>>>>>>>> >>>>>>>>>>> On 2/15/22 18:12, Dmitry Vyukov wrote: >>>>>>>>>>>> On Wed, 2 Feb 2022 at 14:18, Alexandre Ghiti >>>>>>>>>>>> <alexandre.ghiti@canonical.com> wrote: >>>>>>>>>>>>> Hi Aleksandr, >>>>>>>>>>>>> >>>>>>>>>>>>> On Wed, Feb 2, 2022 at 12:08 PM Aleksandr Nogikh <nogikh@google.com> wrote: >>>>>>>>>>>>>> Hello, >>>>>>>>>>>>>> >>>>>>>>>>>>>> syzbot has already not been able to fuzz its RISC-V instance for 97 >>>>>>>>>>>>> That's a longtime, I'll take a look more regularly. >>>>>>>>>>>>> >>>>>>>>>>>>>> days now because the compiled kernel cannot boot. I bisected the issue >>>>>>>>>>>>>> to the following commit: >>>>>>>>>>>>>> >>>>>>>>>>>>>> commit 54c5639d8f507ebefa814f574cb6f763033a72a5 >>>>>>>>>>>>>> Author: Alexandre Ghiti <alexandre.ghiti@canonical.com> >>>>>>>>>>>>>> Date: Fri Oct 29 06:59:27 2021 +0200 >>>>>>>>>>>>>> >>>>>>>>>>>>>> riscv: Fix asan-stack clang build >>>>>>>>>>>>>> >>>>>>>>>>>>>> Apparently, the problem appears on GCC-built RISC-V kernels with KASAN >>>>>>>>>>>>>> enabled. In the previous message syzbot mentions >>>>>>>>>>>>>> "riscv64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU >>>>>>>>>>>>>> Binutils for Debian) 2.35.2", but the issue also reproduces finely on >>>>>>>>>>>>>> a newer GCC compiler: "riscv64-linux-gnu-gcc (Debian 11.2.0-10) >>>>>>>>>>>>>> 11.2.0, GNU ld (GNU Binutils for Debian) 2.37". >>>>>>>>>>>>>> For convenience, I also duplicate the .config file from the bot's >>>>>>>>>>>>>> message: https://syzkaller.appspot.com/x/.config?x=522544a2e0ef2a7d >>>>>>>>>>>>>> >>>>>>>>>>>>>> Can someone with KASAN and RISC-V expertise please take a look? >>>>>>>>>>>>> I'll take a look at that today. >>>>>>>>>>>>> >>>>>>>>>>>>> Thanks for reporting the issue, >>>>>>>>>>> I took a quick look, not enough to fix it but I know the issue comes >>>>>>>>>>> from the inline instrumentation, I have no problem with the outline >>>>>>>>>>> instrumentation. I need to find some cycles to work on this, my goal is >>>>>>>>>>> to fix this for 5.17. >>>>>>>>>> Thanks for the update! >>>>>>>>>> >>>>>>>>>> Can you please share the .config with which you tested the outline >>>>>>>>>> instrumentation? >>>>>>>>>> I updated the syzbot config to use KASAN_OUTLINE instead of KASAN_INLINE, >>>>>>>>>> but it still does not boot :( >>>>>>>>>> >>>>>>>>>> Here's what I used: >>>>>>>>>> https://gist.github.com/a-nogikh/279c85c2d24f47efcc3e865c08844138 >>>>>>>>> Update: it doesn't boot with that big config, but boots if I generate >>>>>>>>> a simple one with KASAN_OUTLINE: >>>>>>>>> >>>>>>>>> make defconfig ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- >>>>>>>>> ./scripts/config -e KASAN -e KASAN_OUTLINE >>>>>>>>> make olddefconfig ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- >>>>>>>>> >>>>>>>>> And it indeed doesn't work if I use KASAN_INLINE. >>>>>>>> It may be an issue with code size. Full syzbot config + KASAN + KCOV >>>>>>>> produce hugely massive .text. It may be hitting some limitation in the >>>>>>>> bootloader/kernel bootstrap code. >>>>> I took a quick glance and it traps on a KASAN address that is not >>>>> mapped, either because it is too soon or because the mapping failed >>>>> somehow. >>>>> >>>>> I'll definitely dive into that tomorrow, sorry for being slow here and >>>>> thanks again for all your work, that helps a lot. >>>>> >>>>> Thanks, >>>>> >>>>> Alex >>>>> >>>>>>> I bisected the difference between the config we use on syzbot and the >>>>>>> simple one that was generated like I described above. >>>>>>> Turns out that it's the DEBUG_VIRTUAL config that makes the difference. >>>>>>> >>>>>>> make defconfig ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- >>>>>>> ./scripts/config -e KASAN -e KASAN_OUTLINE -e DEBUG_VIRTUAL >>>>>>> make olddefconfig ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- >>>>>>> >>>>>>> And the resulting kernel does not boot. >>>>>>> My env: the `riscv/fixes` branch, commit >>>>>>> 6df2a016c0c8a3d0933ef33dd192ea6606b115e3, qemu 6.2.0. >>>> I fixed a few things today: KASAN + SPARSE_VMEMMAP, DEBUG_VIRTUAL and >>>> maybe KASAN + KCOV. >>>> >>>> With those small fixes, I was able to boot your large dotconfig with >>>> KASAN_OUTLINE, the inline version still fails, this is my next target >>>> :) >>>> I'll push that tomorrow! >>> Awesome, thank you very much! >>> Looking forward to finally seeing the instance run :) >> I sent a patchset which should fix your config with *outline* instrumentation. > Was this fix merged? The riscv instance still does not boot: > https://syzkaller.appspot.com/bug?id=5f2ff52ad42cba9f222202219baebd4e63e35127
Yes it has been in Linus tree since 5.18-rc1. I'll take a look at that this week.
Thanks,
Alex
> >> However, as you'll see in the cover letter, I have an issue with >> another KASAN config and if you can take a look at the stacktrace and >> see if that rings a bell, that would be great. >> >> Don't hesitate next time to ping me when the riscv syzbot instance fails :) >> >> Alex >> >> >>> -- >>> Best Regards, >>> Aleksandr >>> >>>> Thanks again, >>>> >>>> Alex >> -- >> 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@googlegroups.com. >> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/CA%2BzEjCtB0rTuNAJkrM2q3JQL7D-9fAXBo0Ud0w__gy9CAfo_Ag%40mail.gmail.com.
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