Re: [PATCH mm v3 25/38] kasan, vmalloc, arm64: mark vmalloc mappings as pgprot_tagged

[Catalin Marinas <catalin.marinas@xxxxxxx>]

On Mon, Dec 13, 2021 at 10:54:21PM +0100, andrey.konovalov@xxxxxxxxx wrote:
> diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
> index b9185503feae..3d35adf365bf 100644
> --- a/arch/arm64/include/asm/vmalloc.h
> +++ b/arch/arm64/include/asm/vmalloc.h
> @@ -25,4 +25,14 @@ static inline bool arch_vmap_pmd_supported(pgprot_t prot)
>  
>  #endif
>  
> +#define arch_vmalloc_pgprot_modify arch_vmalloc_pgprot_modify
> +static inline pgprot_t arch_vmalloc_pgprot_modify(pgprot_t prot)
> +{
> +	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS) &&
> +			(pgprot_val(prot) == pgprot_val(PAGE_KERNEL)))
> +		prot = pgprot_tagged(prot);
> +
> +	return prot;
> +}
> +
>  #endif /* _ASM_ARM64_VMALLOC_H */
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 28becb10d013..760caeedd749 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -115,6 +115,13 @@ static inline int arch_vmap_pte_supported_shift(unsigned long size)
>  }
>  #endif
>  
> +#ifndef arch_vmalloc_pgprot_modify
> +static inline pgprot_t arch_vmalloc_pgprot_modify(pgprot_t prot)
> +{
> +	return prot;
> +}
> +#endif
> +
>  /*
>   *	Highlevel APIs for driver use
>   */
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 837ed355bfc6..58bd2f7f86d7 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3060,6 +3060,8 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
>  		return NULL;
>  	}
>  
> +	prot = arch_vmalloc_pgprot_modify(prot);
> +
>  	if (vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP)) {
>  		unsigned long size_per_node;

I wonder whether we could fix the prot bits in the caller instead and we
won't need to worry about the exec or the module_alloc() case. Something
like:

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d2a00ad4e1dd..4e8c61255b92 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3112,7 +3112,7 @@ void *__vmalloc_node(unsigned long size, unsigned long align,
 			    gfp_t gfp_mask, int node, const void *caller)
 {
 	return __vmalloc_node_range(size, align, VMALLOC_START, VMALLOC_END,
-				gfp_mask, PAGE_KERNEL, 0, node, caller);
+			gfp_mask, pgprot_hwasan(PAGE_KERNEL), 0, node, caller);
 }
 /*
  * This is only for performance analysis of vmalloc and stress purpose.
@@ -3161,7 +3161,7 @@ EXPORT_SYMBOL(vmalloc);
 void *vmalloc_no_huge(unsigned long size)
 {
 	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
-				    GFP_KERNEL, PAGE_KERNEL, VM_NO_HUGE_VMAP,
+				    GFP_KERNEL, pgprot_hwasan(PAGE_KERNEL), VM_NO_HUGE_VMAP,
 				    NUMA_NO_NODE, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(vmalloc_no_huge);

with pgprot_hwasan() defined to pgprot_tagged() only if KASAN_HW_TAGS is
enabled.

-- 
Catalin