Messages in this thread | | | From | Alexandre Ghiti <> | Date | Fri, 18 Feb 2022 14:45:04 +0100 | Subject | Re: [syzbot] riscv/fixes boot error: can't ssh into the instance |
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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.
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
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