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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Sat, 28 May 2022 10:31:16 +0200
Message-ID: <CACT4Y+bP+U2Co67SJG4qri=qHqCk38cq_JwGmo7m0s-8hCF8ww@mail.gmail.com>
Subject: Re: [syzbot] riscv/fixes test error: lost connection to test machine
To:     Alexandre Ghiti <alex@ghiti.fr>
Cc:     Alexandre Ghiti <alexandre.ghiti@canonical.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        syzbot <syzbot+2c5da6a0a16a0c4f34aa@syzkaller.appspotmail.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>
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On Sat, 28 May 2022 at 10:09, Alexandre Ghiti <alex@ghiti.fr> wrote:
>
> On 5/27/22 19:12, Dmitry Vyukov wrote:
> > On Fri, 27 May 2022 at 19:04, Dmitry Vyukov <dvyukov@google.com> wrote:
> >> On Fri, 27 May 2022 at 16:01, Alexandre Ghiti
> >> <alexandre.ghiti@canonical.com> wrote:
> >>> On Friday, May 27, 2022 at 3:55:24 PM UTC+2 Dmitry Vyukov wrote:
> >>>> On Fri, 27 May 2022 at 15:50, Alexandre Ghiti
> >>>> <alexand...@canonical.com> wrote:
> >>>>> On Friday, May 27, 2022 at 3:02:01 PM UTC+2 Dmitry Vyukov wrote:
> >>>>>> On Fri, 27 May 2022 at 14:55, syzbot
> >>>>>> <syzbot+2c5da6...@syzkaller.appspotmail.com> wrote:
> >>>>>>> Hello,
> >>>>>>>
> >>>>>>> syzbot found the following issue on:
> >>>>>>>
> >>>>>>> HEAD commit: c932edeaf6d6 riscv: dts: microchip: fix gpio1 reg pr=
operty..
> >>>>>>> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/riscv/lin=
ux.git fixes
> >>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=3D1418a=
dd5f00000
> >>>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=3Daa6b57=
02bdf14a17
> >>>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=3D2c5da6a=
0a16a0c4f34aa
> >>>>>>> compiler: riscv64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110=
, GNU ld (GNU Binutils for Debian) 2.35.2
> >>>>>>> userspace arch: riscv64
> >>>>>>>
> >>>>>>> IMPORTANT: if you fix the issue, please add the following tag to =
the commit:
> >>>>>>> Reported-by: syzbot+2c5da6...@syzkaller.appspotmail.com
> >>>>>> The CONFIG_KASAN_VMALLOC allows riscv kernel to boot, but now Go
> >>>>>> processes started crashing with:
> >>>>>>
> >>>>>> 1970/01/01 00:06:55 fuzzer started
> >>>>>> runtime: lfstack.push invalid packing: node=3D0xffffff5908a940 cnt=
=3D0x1
> >>>>>> packed=3D0xffff5908a9400001 -> node=3D0xffff5908a940
> >>>>>> fatal error: lfstack.push
> >>>>>> runtime stack:
> >>>>>> runtime.throw({0x30884c, 0xc})
> >>>>>> /usr/local/go/src/runtime/panic.go:1198 +0x60
> >>>>>> runtime.(*lfstack).push(0xdb3850, 0xffffff5908a940)
> >>>>>> /usr/local/go/src/runtime/lfstack.go:30 +0x1a8
> >>>>>>
> >>>>>> Go runtime tries to shove some data into the upper 16 bits of poin=
ters
> >>>>>> assuming they are unused.
> >>>>>> However, the original pointer node=3D0xffffff5908a940 suggest risc=
v now
> >>>>>> has 56-bit users-space address space?
> >>>>>
> >>>>> Yes, sv57 was merged recently.
> >>>>>
> >>>>>> Documentation/riscv/vm-layout.rst claims 48-bit pointers:
> >>>>>> "
> >>>>>> The RISC-V privileged architecture document states that the 64bit =
addresses
> >>>>>> "must have bits 63=E2=80=9348 all equal to bit 47, or else a page-=
fault exception will
> >>>>>> occur.":
> >>>>>
> >>>>> Thanks for pointing that, I extracted that from the specification b=
efore sv57 was specified, I'll fix that.
> >>>>>
> >>>>> The current kernel code will use sv57 as it is supported and advert=
ised by qemu, and to my knowledge, you can't downgrade to sv48 unless by re=
-compiling qemu using the following:
> >>>>>
> >>>>> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> >>>>> index 6dbe9b541f..a64b50ed75 100644
> >>>>> --- a/target/riscv/csr.c
> >>>>> +++ b/target/riscv/csr.c
> >>>>> @@ -637,7 +637,7 @@ static const char valid_vm_1_10_64[16] =3D {
> >>>>> [VM_1_10_MBARE] =3D 1,
> >>>>> [VM_1_10_SV39] =3D 1,
> >>>>> [VM_1_10_SV48] =3D 1,
> >>>>> - [VM_1_10_SV57] =3D 1
> >>>>> + [VM_1_10_SV57] =3D 0
> >>>>> };
> >>>>>
> >>>>> /* Machine Information Registers */
> >>>>>
> >>>>>> ...
> >>>>>> 0000000000000000 | 0 | 0000003fffffffff | 256 GB |
> >>>>>> user-space virtual memory, different per mm
> >>>>>> "
> >>>> There is no kernel config to force SV48/39, right?
> >>>
> >>> No, we rely on what the hardware advertises, if it supports sv57, we'=
ll go for sv57, if not, we'll try sv48...etc. I had some patches to force t=
he downgrade by using the device tree but they never got merged though.
> >> +original CC list
> >>
> >> FTR sent Go runtime change to support SV57:
> >> https://go-review.googlesource.com/c/go/+/409055
> >
> >
> > Is CONFIG_CMDLINE broken on riscv?
> > I am running with:
> >
> > CONFIG_CMDLINE=3D"earlyprintk=3Dserial net.ifnames=3D0
> > sysctl.kernel.hung_task_all_cpu_backtrace=3D1 ima_policy=3Dtcb
> > nf-conntrack-ftp.ports=3D20000 nf-conntrack-tftp.ports=3D20000
> > nf-conntrack-sip.ports=3D20000 nf-conntrack-irc.ports=3D20000
> > nf-conntrack-sane.ports=3D20000 binder.debug_mask=3D0
> > rcupdate.rcu_expedited=3D1 no_hash_pointers page_owner=3Don
> > sysctl.vm.nr_hugepages=3D4 sysctl.vm.nr_overcommit_hugepages=3D4
> > secretmem.enable=3D1 sysctl.max_rcu_stall_to_panic=3D1
> > msr.allow_writes=3Doff dummy_hcd.num=3D2 smp.csd_lock_timeout=3D300000
> > watchdog_thresh=3D165 workqueue.watchdog_thresh=3D420
> > sysctl.net.core.netdev_unregister_timeout_secs=3D420 panic_on_warn=3D1"
>
>
> This command line is 608-character long, but we are still stuck with the
> default COMMAND_LINE_SIZE to 512, I imagine that it is the problem. I
> had proposed a patch last year to bump that to 1024, but it never got
> merged
> https://lore.kernel.org/lkml/CAEn-LTqTXCEC=3DbXTvGyo8SNL0JMWRKtiSwQB7R=3D=
Pc4uhxZUruA@mail.gmail.com/T/#m4b45019dc0f5573f2a50c1f6007c5109fa35efff


risc-v maintainers, please merge it now.
I would even suggest 2048:

git grep "define COMMAND_LINE_SIZE" arch/
arch/alpha/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE   256
arch/arc/include/asm/setup.h:#define COMMAND_LINE_SIZE 256
arch/arm/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 1024
arch/arm64/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE   2048
arch/ia64/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE    2048
arch/m68k/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 256
arch/microblaze/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE      256
arch/mips/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE    4096
arch/parisc/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE  1024
arch/powerpc/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 2048
arch/s390/include/asm/setup.h:#define COMMAND_LINE_SIZE CONFIG_COMMAND_LINE=
_SIZE
arch/sparc/include/uapi/asm/setup.h:# define COMMAND_LINE_SIZE 2048
arch/sparc/include/uapi/asm/setup.h:# define COMMAND_LINE_SIZE 256
arch/um/include/asm/setup.h:#define COMMAND_LINE_SIZE 4096
arch/x86/include/asm/setup.h:#define COMMAND_LINE_SIZE 2048
arch/xtensa/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE  256


It's also interesting how the kernel handles overflow. Imagine one
adds that_critical_security_feature=3D1 to the end of an existing long
line.