linux-kernel - Re: [PATCH v2 08/10] powerpc/fsl_booke/kaslr: clear the original kernel if randomized

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Message-ID: <fc1bf072-8256-f944-cc60-f0da50d319ff@c-s.fr>
Date:   Tue, 30 Jul 2019 11:47:34 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Jason Yan <yanaijie@...wei.com>, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com,
        benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        keescook@...omium.org, kernel-hardening@...ts.openwall.com
Cc:     linux-kernel@...r.kernel.org, wangkefeng.wang@...wei.com,
        yebin10@...wei.com, thunder.leizhen@...wei.com,
        jingxiangfeng@...wei.com, fanchengyang@...wei.com,
        zhaohongjiang@...wei.com
Subject: Re: [PATCH v2 08/10] powerpc/fsl_booke/kaslr: clear the original
 kernel if randomized



Le 30/07/2019 à 09:42, Jason Yan a écrit :
> The original kernel still exists in the memory, clear it now.
> 
> Signed-off-by: Jason Yan <yanaijie@...wei.com>
> Cc: Diana Craciun <diana.craciun@....com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@....fr>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Kees Cook <keescook@...omium.org>

Reviewed-by: Christophe Leroy <christophe.leroy@....fr>

Is kaslr_second_init() the best name ?
What about kaslr_late_init() or kaslr_clear_early_kernel() or ... ?

Christophe

> ---
>   arch/powerpc/kernel/kaslr_booke.c  | 11 +++++++++++
>   arch/powerpc/mm/mmu_decl.h         |  2 ++
>   arch/powerpc/mm/nohash/fsl_booke.c |  1 +
>   3 files changed, 14 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kaslr_booke.c
> index 0bb02e45b928..f032ac119457 100644
> --- a/arch/powerpc/kernel/kaslr_booke.c
> +++ b/arch/powerpc/kernel/kaslr_booke.c
> @@ -412,3 +412,14 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
>   
>   	reloc_kernel_entry(dt_ptr, kimage_vaddr);
>   }
> +
> +void __init kaslr_second_init(void)
> +{
> +	/* If randomized, clear the original kernel */
> +	if (kimage_vaddr != KERNELBASE) {
> +		unsigned long kernel_sz;
> +
> +		kernel_sz = (unsigned long)_end - kimage_vaddr;
> +		memzero_explicit((void *)KERNELBASE, kernel_sz);
> +	}
> +}
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index 9332772c8a66..550c8d742f88 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -150,8 +150,10 @@ extern void loadcam_multi(int first_idx, int num, int tmp_idx);
>   
>   #ifdef CONFIG_RANDOMIZE_BASE
>   void kaslr_early_init(void *dt_ptr, phys_addr_t size);
> +void kaslr_second_init(void);
>   #else
>   static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
> +static inline void kaslr_second_init(void) {}
>   #endif
>   
>   struct tlbcam {
> diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/fsl_booke.c
> index 8d25a8dc965f..fa5a87f5c08e 100644
> --- a/arch/powerpc/mm/nohash/fsl_booke.c
> +++ b/arch/powerpc/mm/nohash/fsl_booke.c
> @@ -269,6 +269,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
>   	kernstart_addr = start;
>   	if (is_second_reloc) {
>   		virt_phys_offset = PAGE_OFFSET - memstart_addr;
> +		kaslr_second_init();
>   		return;
>   	}
>   
>