On Tue, 15 Oct 2024 at 23:37, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>
> When sync:ing the VMALLOC area to other CPUs, make sure to also
> sync the KASAN shadow memory for the VMALLOC area, so that we
> don't get stale entries for the shadow memory in the top level PGD.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 565cbaad83d8 ("ARM: 9202/1: kasan: support CONFIG_KASAN_VMALLOC")
> Link: https://lore.kernel.org/linux-arm-kernel/a1a1d062-f3a2-4d05-9836-3b098de9db6d@xxxxxxxxxxx/
> Reported-by: Clement LE GOFFIC <clement.legoffic@xxxxxxxxxxx>
> Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> arch/arm/mm/ioremap.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
> index 794cfea9f9d4..449f1f04814c 100644
> --- a/arch/arm/mm/ioremap.c
> +++ b/arch/arm/mm/ioremap.c
> @@ -23,6 +23,7 @@
> */
> #include <linux/module.h>
> #include <linux/errno.h>
> +#include <linux/kasan.h>
> #include <linux/mm.h>
> #include <linux/vmalloc.h>
> #include <linux/io.h>
> @@ -125,6 +126,12 @@ void __check_vmalloc_seq(struct mm_struct *mm)
> pgd_offset_k(VMALLOC_START),
> sizeof(pgd_t) * (pgd_index(VMALLOC_END) -
> pgd_index(VMALLOC_START)));
> + if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
> + memcpy(pgd_offset(mm, (unsigned long)kasan_mem_to_shadow((void *)VMALLOC_START)),
> + pgd_offset_k((unsigned long)kasan_mem_to_shadow((void *)VMALLOC_START)),
> + sizeof(pgd_t) * (pgd_index((unsigned long)kasan_mem_to_shadow((void *)VMALLOC_END)) -
> + pgd_index((unsigned long)kasan_mem_to_shadow((void *)VMALLOC_START))));
> + }
+1 to Russell's suggestion to change this wall of text into something legible.
Then, there is another part to this: in arch/arm/kernel/traps.c, we
have the following code
void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
{
if (start < VMALLOC_END && end > VMALLOC_START)
atomic_inc_return_release(&init_mm.context.vmalloc_seq);
}
where we only bump vmalloc_seq if the updated region overlaps with the
vmalloc region, so this will need a similar treatment afaict.
