Re: [PATCH 0/6] RISC-V kasan rework

Conor Dooley
2022-12-22T22:01:55Z

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Hey Alex!

On Fri, Dec 16, 2022 at 05:21:35PM +0100, Alexandre Ghiti wrote:
> As described in patch 2, our current kasan implementation is intricate,
> so I tried to simplify the implementation and mimic what arm64/x86 are
> doing.

I'm not sure that I am going to have much to contribute for this series,
but I did notice some difficulty actually applying it. At whatever point
you sent it, the pwbot did actually give it a shakedown - but it doesn't
apply any of the "usual suspects" tree wise.
It looks like multiple patches interact with commit 9f2ac64d6ca6 ("riscv:
mm: add missing memcpy in kasan_init"), which caused me some difficulty
that was not just a trivial resolution.
A rebase on top of v6.2-rc1 is (I would imagine) a good idea for this
series?

For the future, perhaps using the base-commit arg would be useful for
stuff like this :)

> In addition it fixes UEFI bootflow with a kasan kernel and kasan inline
> instrumentation: all kasan configurations were tested on a large ubuntu
> kernel with success with KASAN_KUNIT_TEST and KASAN_MODULE_TEST.
>
> inline ubuntu config + uefi:
> sv39: OK
> sv48: OK
> sv57: OK
>
> outline ubuntu config + uefi:
> sv39: OK
> sv48: OK
> sv57: OK
>
> Actually 1 test always fails with KASAN_KUNIT_TEST that I have to check:
> # kasan_bitops_generic: EXPECTATION FAILED at mm/kasan/kasan__test.c:1020
> KASAN failure expected in "set_bit(nr, addr)", but none occurrred
>
> Note that Palmer recently proposed to remove COMMAND_LINE_SIZE from the
> userspace abi
> https://lore.kernel.org/lkml/20221211061358.28035-1-palmer@rivosinc.com/T/
> so that we can finally increase the command line to fit all kasan kernel
> parameters.
>
> All of this should hopefully fix the syzkaller riscv build that has been
> failing for a few months now, any test is appreciated and if I can help
> in any way, please ask.
>
> Alexandre Ghiti (6):
> riscv: Split early and final KASAN population functions
> riscv: Rework kasan population functions
> riscv: Move DTB_EARLY_BASE_VA to the kernel address space
> riscv: Fix EFI stub usage of KASAN instrumented string functions
> riscv: Fix ptdump when KASAN is enabled
> riscv: Unconditionnally select KASAN_VMALLOC if KASAN
>
> arch/riscv/Kconfig | 1 +
> arch/riscv/kernel/image-vars.h | 8 -
> arch/riscv/mm/init.c | 2 +-
> arch/riscv/mm/kasan_init.c | 511 ++++++++++++++------------
> arch/riscv/mm/ptdump.c | 24 +-
> drivers/firmware/efi/libstub/Makefile | 7 +-
> drivers/firmware/efi/libstub/string.c | 133 +++++++
> 7 files changed, 435 insertions(+), 251 deletions(-)
>
> --
> 2.37.2
>
>

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