Re: [PATCH 0/6] PowerPc 8xx TLB/MMU fixes

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> > No, use get_user() not __get_user() or if you use the later, also use
> > access_ok(), and test the result in case it errors (if it does, you
> > probably want to just goto bad access and SEGV).
> 
> OK, lets see what this gives us:

Hrm... did you change anything ? :-)

Ben.

> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index c33c6de..1bf91d3 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -153,7 +153,8 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  #ifdef DEBUG_DCBX
>  		const char *istr = NULL;
> 
> -		insn = *((unsigned long *)regs->nip);
> +		insn = 0;
> +		__get_user(insn, (unsigned long __user *)regs->nip);
>  		if (((insn >> (31-5)) & 0x3f) == 31) {
>  			if (((insn >> 1) & 0x3ff) == 1014) /* dcbz ? 0x3f6 */
>  				istr = "dcbz";
> @@ -171,27 +172,32 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  				dar = regs->gpr[rb];
>  				if (ra)
>  					dar += regs->gpr[ra];
> -				if (dar != address && address != 0x00f0 && trap == 0x300)
> +				if (dar != address && trap == 0x300)
>  					printk(KERN_CRIT "%s: address:%lx, dar:%lx!\n", istr, address, dar);
>  				if (!strcmp(istr, "dcbst") && is_write) {
>  					printk(KERN_CRIT "dcbst R%ld,R%ld = %lx as a store, fixing!\n",
>  					       ra, rb, dar);
>  					is_write = 0;
>  				}
> -
> +#if 0
>  				if (trap == 0x300 && address != dar) {
>  					__asm__ ("mtdar %0" : : "r" (dar));
>  					return 0;
>  				}
> +#endif
>  			}
>  		}
>  #endif
>  		if (address == 0x00f0 && trap == 0x300) {
> -			pte_t *ptep;
> +			//pte_t *ptep;
> 
>  			/* This is from a dcbX or icbi insn gone bad, these
>  			 * insn do not set DAR so we have to do it here instead */
> -			insn = *((unsigned long *)regs->nip);
> +			if (get_user(insn, (unsigned long __user *)regs->nip)) {
> +				printk(KERN_CRIT "get_user failed, NIP:%lx\n",
> +				       regs->nip);
> +				goto bad_area_nosemaphore;
> +			}
> 
>  			ra = (insn >> (31-15)) & 0x1f; /* Reg RA */
>  			rb = (insn >> (31-20)) & 0x1f; /* Reg RB */
> @@ -206,7 +212,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  			       trap, address, dar, error_code, istr);
>  #endif
>  			address = dar;
> -#if 1
> +#if 0
>  			if (is_write && get_pteptr(mm, dar, &ptep, NULL)) {
>  				pte_t my_pte = *ptep;
> 
> @@ -216,7 +222,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  				}
>  			}
>  #else
> -			return 0;
> +			//return 0;
>  #endif
>  		}
>  	}