[PATCH v2 0/2] Fix KASAN crash when using KASAN_VMALLOC

[Linus Walleij]

This problem reported by Clement LE GOFFIC manifest when
using CONFIG_KASAN_IN_VMALLOC and VMAP_STACK:
https://lore.kernel.org/linux-arm-kernel/a1a1d062-f3a2-4d05-9836-3b098de9db6d@foss.st.com/

After some analysis it seems we are missing to sync the
VMALLOC shadow memory in top level PGD to all CPUs.

Add some code to perform this sync, and the bug appears
to go away.

As suggested by Ard, also perform a dummy read from the
shadow memory of the new VMAP_STACK in the low level
assembly.

Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
Changes in v2:
- Implement the two helper functions suggested by Russell
  making the KASAN PGD copying less messy.
- Link to v1: https://lore.kernel.org/r/20241015-arm-kasan-vmalloc-crash-v1-0-dbb23592ca83@linaro.org

---
Linus Walleij (2):
      ARM: ioremap: Sync PGDs for VMALLOC shadow
      ARM: entry: Do a dummy read from VMAP shadow

 arch/arm/kernel/entry-armv.S |  8 ++++++++
 arch/arm/mm/ioremap.c        | 25 +++++++++++++++++++++----
 2 files changed, 29 insertions(+), 4 deletions(-)
---
base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
change-id: 20241015-arm-kasan-vmalloc-crash-fcbd51416457

Best regards,
-- 
Linus Walleij <linus.walleij at linaro.org>