linux-kernel - Re: [PATCH V4 Resend] ZBOOT: fix stack protector in compressed boot phase

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Date:   Wed, 28 Mar 2018 13:59:52 -0400
From:   Rich Felker <dalias@...c.org>
To:     Huacai Chen <chenhc@...ote.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <james.hogan@...s.com>, linux-mips@...ux-mips.org,
        Russell King <linux@....linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        linux-sh@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH V4 Resend] ZBOOT: fix stack protector in compressed boot
 phase

On Wed, Mar 28, 2018 at 04:48:53PM +0800, Huacai Chen wrote:
> Call __stack_chk_guard_setup() in decompress_kernel() is too late that
> stack checking always fails for decompress_kernel() itself. So remove
> __stack_chk_guard_setup() and initialize __stack_chk_guard before we
> call decompress_kernel().
> 
> Original code comes from ARM but also used for MIPS and SH, so fix them
> together. If without this fix, compressed booting of these archs will
> fail because stack checking is enabled by default (>=4.16).
> 
> V1 -> V2: Fix build on ARM.
> V2 -> V3: Fix build on SuperH.
> V3 -> V4: Initialize __stack_chk_guard in C code as a constant.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Huacai Chen <chenhc@...ote.com>
> ---
>  arch/arm/boot/compressed/misc.c        | 9 +--------
>  arch/mips/boot/compressed/decompress.c | 9 +--------
>  arch/sh/boot/compressed/misc.c         | 9 +--------
>  3 files changed, 3 insertions(+), 24 deletions(-)
> 
> [...]
> 
> diff --git a/arch/sh/boot/compressed/misc.c b/arch/sh/boot/compressed/misc.c
> index 627ce8e..c15cac9 100644
> --- a/arch/sh/boot/compressed/misc.c
> +++ b/arch/sh/boot/compressed/misc.c
> @@ -104,12 +104,7 @@ static void error(char *x)
>  	while(1);	/* Halt */
>  }
>  
> -unsigned long __stack_chk_guard;
> -
> -void __stack_chk_guard_setup(void)
> -{
> -	__stack_chk_guard = 0x000a0dff;
> -}
> +const unsigned long __stack_chk_guard = 0x000a0dff;
>  
>  void __stack_chk_fail(void)
>  {
> @@ -130,8 +125,6 @@ void decompress_kernel(void)
>  {
>  	unsigned long output_addr;
>  
> -	__stack_chk_guard_setup();
> -
>  #ifdef CONFIG_SUPERH64
>  	output_addr = (CONFIG_MEMORY_START + 0x2000);
>  #else
> -- 
> 2.7.0

LGTM.

Acked-by: Rich Felker <dalias@...c.org>

Rich