linux-kernel - Re: Sparc miss chance to fix recoverable fault in copy_from

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Message-Id: <20090813.124838.210334778.davem@davemloft.net>
Date:	Thu, 13 Aug 2009 12:48:38 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	heyongli@...il.com
Cc:	linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: Sparc miss chance to fix recoverable fault in copy_from_user

From: hyl <heyongli@...il.com>
Date: Wed, 12 Aug 2009 09:53:01 +0800

Please post all Sparc patches and questions CC:'d to
sparclinux@...r.kernel.org otherwise no Sparc experts are going to see
it.

> --- a/arch/sparc/kernel/sun4v_tlb_miss.S
> +++ b/arch/sparc/kernel/sun4v_tlb_miss.S
> @@ -124,7 +124,7 @@ sun4v_dtlb_load:
>  	mov	%g3, %o2		! PTE
>  	mov	HV_MMU_DMMU, %o3	! flags
>  	ta	HV_MMU_MAP_ADDR_TRAP
> -	brnz,pn	%o0, sun4v_dtlb_error
> +	brnz,pn	%o0, sun4v_dtlb_prot
>  	 mov	%g2, %o1		! restore %o1
>  	mov	%g1, %o0		! restore %o0
>  	mov	%g5, %o2		! restore %o2
> 
> 
> 
> am i miss understanding the merged sparc/spar64?
> 
> this problem found on sparc64, via a simple module just access address 0
> via copy_from_user. another simple test is kgdb, issue a cmd:
> x 0

That condition should never trigger, the problem is caused
elsewhere.

If the HV_MMU_MAP_ADDR_TRAP hypervisor call gives an error it means:

1) The PTE passed in is invalid

2) The PTE passed in translates to addresses outside of the
   range accessible to the guest

3) The virtual address is invalid

And the kernel should never have such an illegal address or
PTE mapping here.

You need to figure out how the bad mapping gets into the kernel page
tables and/or translations in the first place.
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