[syzbot] riscv/fixes test error: lost connection to test machine

Sat May 28 01:31:16 PDT 2022

On Sat, 28 May 2022 at 10:09, Alexandre Ghiti <alex at ghiti.fr> wrote:
>
> On 5/27/22 19:12, Dmitry Vyukov wrote:
> > On Fri, 27 May 2022 at 19:04, Dmitry Vyukov <dvyukov at google.com> wrote:
> >> On Fri, 27 May 2022 at 16:01, Alexandre Ghiti
> >> <alexandre.ghiti at 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... at 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... at syzkaller.appspotmail.com> wrote:
> >>>>>>> Hello,
> >>>>>>>
> >>>>>>> syzbot found the following issue on:
> >>>>>>>
> >>>>>>> HEAD commit: c932edeaf6d6 riscv: dts: microchip: fix gpio1 reg property..
> >>>>>>> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes
> >>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1418add5f00000
> >>>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=aa6b5702bdf14a17
> >>>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=2c5da6a0a16a0c4f34aa
> >>>>>>> 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... at 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=0xffffff5908a940 cnt=0x1
> >>>>>> packed=0xffff5908a9400001 -> node=0xffff5908a940
> >>>>>> 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 pointers
> >>>>>> assuming they are unused.
> >>>>>> However, the original pointer node=0xffffff5908a940 suggest riscv 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 63–48 all equal to bit 47, or else a page-fault exception will
> >>>>>> occur.":
> >>>>>
> >>>>> Thanks for pointing that, I extracted that from the specification before sv57 was specified, I'll fix that.
> >>>>>
> >>>>> The current kernel code will use sv57 as it is supported and advertised 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] = {
> >>>>> [VM_1_10_MBARE] = 1,
> >>>>> [VM_1_10_SV39] = 1,
> >>>>> [VM_1_10_SV48] = 1,
> >>>>> - [VM_1_10_SV57] = 1
> >>>>> + [VM_1_10_SV57] = 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 the 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="earlyprintk=serial net.ifnames=0
> > sysctl.kernel.hung_task_all_cpu_backtrace=1 ima_policy=tcb
> > nf-conntrack-ftp.ports=20000 nf-conntrack-tftp.ports=20000
> > nf-conntrack-sip.ports=20000 nf-conntrack-irc.ports=20000
> > nf-conntrack-sane.ports=20000 binder.debug_mask=0
> > rcupdate.rcu_expedited=1 no_hash_pointers page_owner=on
> > sysctl.vm.nr_hugepages=4 sysctl.vm.nr_overcommit_hugepages=4
> > secretmem.enable=1 sysctl.max_rcu_stall_to_panic=1
> > msr.allow_writes=off dummy_hcd.num=2 smp.csd_lock_timeout=300000
> > watchdog_thresh=165 workqueue.watchdog_thresh=420
> > sysctl.net.core.netdev_unregister_timeout_secs=420 panic_on_warn=1"
>
>
> 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=bXTvGyo8SNL0JMWRKtiSwQB7R=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=1 to the end of an existing long
line.