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    SubjectRe: [syzbot] riscv/fixes boot error: can't ssh into the instance
    On Fri, 27 May 2022 at 09:33, Alexandre Ghiti
    <alexandre.ghiti@canonical.com> wrote:
    >
    > Hi Atish,
    > > > > 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.
    > > > >
    > > >
    > > > Are you seeing this error or a different one ? I used the
    > > > syzkaller_defconfig from the patch below on v5.18.
    > > >
    > > > https://lore.kernel.org/all/20220419174952.699-1-palmer@rivosinc.com/
    > > >
    > > > [ 15.076116][ T1] Mandatory Access Control activated.
    > > > [ 15.158241][ T1] AppArmor: AppArmor Filesystem Enabled
    > > > [ 16.150870][ T1] NET: Registered PF_INET protocol family
    > > > [ 16.166167][ T1] IP idents hash table entries: 32768 (order: 6,
    > > > 262144 bytes, linear)
    > > > [ 16.188727][ T1] Unable to handle kernel paging request at
    > > > virtual address ffebfffeffff2000
    > > > [ 16.192727][ T1] Oops [#1]
    > > > [ 16.193479][ T1] Modules linked in:
    > > > [ 16.194687][ T1] CPU: 3 PID: 1 Comm: swapper/0 Not tainted
    > > > 5.18.0-00001-g37ac279268bf-dirty #9
    > > > [ 16.196486][ T1] Hardware name: riscv-virtio,qemu (DT)
    > > > [ 16.197836][ T1] epc : kasan_check_range+0x9e/0x14e
    > > > [ 16.199104][ T1] ra : memset+0x1e/0x4c
    > > > [ 16.200091][ T1] epc : ffffffff804787e0 ra : ffffffff80478f30 sp
    > > > : ff600000073ffb70
    > > > [ 16.201420][ T1] gp : ffffffff85879e80 tp : ff600000073f0000 t0
    > > > : 7300000000000000
    > > > [ 16.202762][ T1] t1 : ffebfffeffff21ff t2 : 73746e6564692050 s0
    > > > : ff600000073ffba0
    > > > [ 16.204047][ T1] s1 : 0000000000001000 a0 : ffebfffeffff2200 a1
    > > > : 0000000000001000
    > > > [ 16.205312][ T1] a2 : 0000000000000001 a3 : ffffffff803a4f32 a4
    > > > : ff5ffffffff90000
    > > > [ 16.206592][ T1] a5 : ffebfffeffff2000 a6 : 0000004000000000 a7
    > > > : ff5ffffffff90fff
    > > > [ 16.207865][ T1] s2 : ff5ffffffff90000 s3 : 0000000000000000 s4
    > > > : ffffffff8467ea90
    > > > [ 16.209134][ T1] s5 : 0000000000000000 s6 : ff5ffffffff90000 s7
    > > > : 0000000000000000
    > > > [ 16.210394][ T1] s8 : 0000000000001000 s9 : ffffffff8587ca40
    > > > s10: 0000000000000004
    > > > [ 16.211952][ T1] s11: ffffffff858a03a0 t3 : 0000000000000000 t4
    > > > : 0000000000000040
    > > > [ 16.213469][ T1] t5 : ffebfffeffff2200 t6 : ff600000073ff738
    > > > [ 16.214853][ T1] status: 0000000200000120 badaddr:
    > > > ffebfffeffff2000 cause: 000000000000000d
    > > > [ 16.216910][ T1] Call Trace:
    > > > [ 16.217816][ T1] [<ffffffff803a4f32>] pcpu_alloc+0x844/0x1254
    > > > [ 16.219110][ T1] [<ffffffff803a59a0>] __alloc_percpu+0x28/0x34
    > > > [ 16.220244][ T1] [<ffffffff8328824a>] ip_rt_init+0x17e/0x382
    > > > [ 16.221606][ T1] [<ffffffff8328861c>] ip_init+0x18/0x30
    > > > [ 16.222719][ T1] [<ffffffff8328a0ee>] inet_init+0x2a6/0x550
    > > > [ 16.223863][ T1] [<ffffffff80003204>] do_one_initcall+0x130/0x7dc
    > > > [ 16.225002][ T1] [<ffffffff83201fbc>] kernel_init_freeable+0x510/0x5b4
    > > > [ 16.226273][ T1] [<ffffffff8319842a>] kernel_init+0x28/0x21c
    > > > [ 16.227337][ T1] [<ffffffff80005818>] ret_from_exception+0x0/0x10
    > > > [ 16.229910][ T1] ---[ end trace 0000000000000000 ]---
    > > > [ 16.231880][ T1] Kernel panic - not syncing: Fatal exception
    > > >
    > > >
    > >
    > > Enabling CONFIG_KASAN_VMALLOC=y solves the issue and I am able to boot
    > > to the userspace.
    > > I have tried enabling/disabling CONFIG_VMAP_STACK as well. Both works fine.
    > >
    > > Looking at the ARM64 Kconfig, KASAN_VMALLOC is enabled if KASAN is enabled.
    > > This diff seems to work for me.
    > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
    > > index 00fd9c548f26..cbf0fe227c77 100644
    > > --- a/arch/riscv/Kconfig
    > > +++ b/arch/riscv/Kconfig
    > > @@ -122,6 +122,7 @@ config RISCV
    > > select TRACE_IRQFLAGS_SUPPORT
    > > select UACCESS_MEMCPY if !MMU
    > > select ZONE_DMA32 if 64BIT
    > > + select KASAN_VMALLOC if KASAN
    > >
    > > I am not a kasan expert so I am not sure if this is the correct fix or
    > > just hides the real issue. pcpu_alloc seems to use vmalloc though.
    >
    > When this type of thing happens, generally this is because of an error
    > in the kasan page table, I'll take a look this time, sorry I did not
    > do this before.
    >
    > Thanks for finding this,
    >
    > Alex

    Unfortunately riscv still does not work for syzbot, other bugs piled up.
    Something has changes wrt user-space pointers:
    https://groups.google.com/g/syzkaller-bugs/c/lU0GQTZoNQQ/m/iuRBTgU3AAAJ
    https://syzkaller.appspot.com/bug?extid=2c5da6a0a16a0c4f34aa

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