linux-kernel - Re: [PATCH] riscv: kasan: Fix MODULES_VADDR evaluation due to local variables' name

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Date:   Fri, 18 Jun 2021 23:58:43 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     jszhang3@...l.ustc.edu.cn
CC:     ryabinin.a.a@...il.com, glider@...gle.com, andreyknvl@...il.com,
        dvyukov@...gle.com, Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, alex@...ti.fr, kasan-dev@...glegroups.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject:     Re: [PATCH] riscv: kasan: Fix MODULES_VADDR evaluation due to local variables' name

On Fri, 18 Jun 2021 07:01:36 PDT (-0700), jszhang3@...l.ustc.edu.cn wrote:
> From: Jisheng Zhang <jszhang@...nel.org>
>
> commit 2bfc6cd81bd1 ("riscv: Move kernel mapping outside of linear
> mapping") makes use of MODULES_VADDR to populate kernel, BPF, modules
> mapping. Currently, MODULES_VADDR is defined as below for RV64:
>
> | #define MODULES_VADDR   (PFN_ALIGN((unsigned long)&_end) - SZ_2G)
>
> But kasan_init() has two local variables which are also named as _start,
> _end, so MODULES_VADDR is evaluated with the local variable _end
> rather than the global "_end" as we expected. Fix this issue by
> renaming the two local variables.
>
> Fixes: 2bfc6cd81bd1 ("riscv: Move kernel mapping outside of linear mapping")
> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> ---
>  arch/riscv/mm/kasan_init.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
> index 55c113345460..d7189c8714a9 100644
> --- a/arch/riscv/mm/kasan_init.c
> +++ b/arch/riscv/mm/kasan_init.c
> @@ -169,7 +169,7 @@ static void __init kasan_shallow_populate(void *start, void *end)
>
>  void __init kasan_init(void)
>  {
> -	phys_addr_t _start, _end;
> +	phys_addr_t p_start, p_end;
>  	u64 i;
>
>  	/*
> @@ -189,9 +189,9 @@ void __init kasan_init(void)
>  			(void *)kasan_mem_to_shadow((void *)VMALLOC_END));
>
>  	/* Populate the linear mapping */
> -	for_each_mem_range(i, &_start, &_end) {
> -		void *start = (void *)__va(_start);
> -		void *end = (void *)__va(_end);
> +	for_each_mem_range(i, &p_start, &p_end) {
> +		void *start = (void *)__va(p_start);
> +		void *end = (void *)__va(p_end);
>
>  		if (start >= end)
>  			break;

Thanks for this.  I'd prefer a cleaner fix for tihs (maybe more '_'s in 
_end?), but I don't think we can do that without touching a bunch of 
code.  Given that this is necessary to make the fix work for me, I'm 
just going to take it as-is.

This is on fixes.