[PATCH] arm64: kasan: avoid bad virt_to_pfn()

[Laura Abbott]

On 03/06/2017 11:06 AM, Mark Rutland wrote:
> Booting a v4.11-rc1 kernel with DEBUG_VIRTUAL and KASAN enabled produces
> the following splat (trimmed for brevity):
> 
> [    0.000000] virt_to_phys used for non-linear address: ffff200008080000 (0xffff200008080000)
> [    0.000000] WARNING: CPU: 0 PID: 0 at arch/arm64/mm/physaddr.c:14 __virt_to_phys+0x48/0x70
> [    0.000000] PC is at __virt_to_phys+0x48/0x70
> [    0.000000] LR is at __virt_to_phys+0x48/0x70
> [    0.000000] Call trace:
> [    0.000000] [<ffff2000080b1ac0>] __virt_to_phys+0x48/0x70
> [    0.000000] [<ffff20000a03b86c>] kasan_init+0x1c0/0x498
> [    0.000000] [<ffff20000a034018>] setup_arch+0x2fc/0x948
> [    0.000000] [<ffff20000a030c68>] start_kernel+0xb8/0x570
> [    0.000000] [<ffff20000a0301e8>] __primary_switched+0x6c/0x74
> 
> This is because we use virt_to_pfn() on a kernel image address when
> trying to figure out its nid, so that we can allocate its shadow from
> the same node.
> 
> As with other recent changes, this patch uses lm_alias() to solve this.
> 
> We could instead use NUMA_NO_NODE, as x86 does for all shadow
> allocations, though we'll likely want the "real" memory shadow to be
> backed from its corresponding nid anyway, so we may as well be
> consistent and find the nid for the image shadow.
> 
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Laura Abbott <labbott at redhat.com>
> Cc: Will Deacon <will.deacon at arm.com>
> ---
>  arch/arm64/mm/kasan_init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 55d1e92..687a358 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -162,7 +162,7 @@ void __init kasan_init(void)
>  	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
>  
>  	vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
> -			 pfn_to_nid(virt_to_pfn(_text)));
> +			 pfn_to_nid(virt_to_pfn(lm_alias(_text))));
>  
>  	/*
>  	 * vmemmap_populate() has populated the shadow region that covers the
> 

Acked-by: Laura Abbott <labbott at redhat.com>