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@xxxxxxxxxxx/ 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@xxxxxxxxxx> --- Changes in v3: - Collect Mark Rutlands ACK on patch 1 - Change the simplified assembly add r2, ip, lsr #n to the canonical add r2, r2, ip, lsr #n in patch 2. - Link to v2: https://lore.kernel.org/r/20241016-arm-kasan-vmalloc-crash-v2-0-0a52fd086eef@xxxxxxxxxx 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@xxxxxxxxxx --- 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@xxxxxxxxxx>
