linux-kernel - Re: [PATCH 2/4] x86: SROP mitigation: implement signal canaries

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Date:	Thu, 15 May 2014 14:31:40 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Erik Bosman <erik@...emu.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] x86: SROP mitigation: implement signal canaries

Erik Bosman <erik@...emu.org> writes:

>  
> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
> index 2206757..1a9285a 100644
> --- a/arch/x86/ia32/ia32_signal.c
> +++ b/arch/x86/ia32/ia32_signal.c
> @@ -212,9 +212,18 @@ asmlinkage long sys32_sigreturn(void)
>  	struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
>  	sigset_t set;
>  	unsigned int ax;
> +#ifdef CONFIG_SIGNAL_CANARY
> +	u32 canary;
> +#endif

Don't you completely break the ABI here? I'm sure there are programs out
there who hard code the offset into the FP state.

I think you either need to put it at the total end or somewhere
currently unused

Besides that I would remove the CONFIG_* once it works and just do it
unconditionally.

-Andi


-- 
ak@...ux.intel.com -- Speaking for myself only
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