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Subject: Re: [PATCH v10 6/6] powerpc: Book3S 64-bit outline-only KASAN support
To:     Daniel Axtens <dja@axtens.net>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
        kasan-dev@googlegroups.com, aneesh.kumar@linux.ibm.com,
        bsingharora@gmail.com
References: <20210203115946.663273-1-dja@axtens.net>
 <20210203115946.663273-7-dja@axtens.net>
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <4b790789-052f-76de-a289-726517026efd@csgroup.eu>
Date:   Wed, 3 Feb 2021 13:45:00 +0100
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Le 03/02/2021 à 12:59, Daniel Axtens a écrit :
> Implement a limited form of KASAN for Book3S 64-bit machines running under
> the Radix MMU, supporting only outline mode.
> 

> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index a66f435dabbf..9a6fd603f0e7 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -2157,8 +2157,8 @@ void show_stack(struct task_struct *tsk, unsigned long *stack,
>   			break;
>   
>   		stack = (unsigned long *) sp;
> -		newsp = stack[0];
> -		ip = stack[STACK_FRAME_LR_SAVE];
> +		newsp = READ_ONCE_NOCHECK(stack[0]);
> +		ip = READ_ONCE_NOCHECK(stack[STACK_FRAME_LR_SAVE]);
>   		if (!firstframe || ip != lr) {
>   			printk("%s["REG"] ["REG"] %pS",
>   				loglvl, sp, ip, (void *)ip);
> @@ -2176,17 +2176,19 @@ void show_stack(struct task_struct *tsk, unsigned long *stack,
>   		 * See if this is an exception frame.
>   		 * We look for the "regshere" marker in the current frame.
>   		 */
> -		if (validate_sp(sp, tsk, STACK_INT_FRAME_SIZE)
> -		    && stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
> +		if (validate_sp(sp, tsk, STACK_INT_FRAME_SIZE) &&
> +		    (READ_ONCE_NOCHECK(stack[STACK_FRAME_MARKER]) ==
> +		     STACK_FRAME_REGS_MARKER)) {
>   			struct pt_regs *regs = (struct pt_regs *)
>   				(sp + STACK_FRAME_OVERHEAD);
>   
> -			lr = regs->link;
> +			lr = READ_ONCE_NOCHECK(regs->link);
>   			printk("%s--- interrupt: %lx at %pS\n",
> -			       loglvl, regs->trap, (void *)regs->nip);
> +			       loglvl, READ_ONCE_NOCHECK(regs->trap),
> +			       (void *)READ_ONCE_NOCHECK(regs->nip));
>   			__show_regs(regs);
>   			printk("%s--- interrupt: %lx\n",
> -			       loglvl, regs->trap);
> +			       loglvl, READ_ONCE_NOCHECK(regs->trap));
>   
>   			firstframe = 1;
>   		}


The above changes look like a bug fix not directly related to KASAN. Should be split out in another 
patch I think.

Christophe