Subject: Re: [PATCH,v2] arm64: fix the illegal address access in some cases

From: Catalin Marinas <[email-masked]>
Date: Mon, 27 Jul 2020 12:47:10 +0100

On Sat, Jul 25, 2020 at 10:08:06AM +0800, guodeqing wrote:
> The ihl value of ip header is smaller than 5 in some cases, if the
> ihl value is smaller than 5, then the next code will access the illegal
> address, and the system will panic. ip_fast_csum() must be able to handle 
> any value that could fit in the ihl field of the ip protocol header.
> 
> Here I add the check of the ihl value to solve this problem.
> 
> Fixes: 0e455d8e80aa (arm64: Implement optimised IP checksum helpers)
> Signed-off-by: guodeqing <[email-masked]>
> ---
>  arch/arm64/include/asm/checksum.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/checksum.h b/arch/arm64/include/asm/checksum.h
> index b6f7bc6..5a7d9ac 100644
> --- a/arch/arm64/include/asm/checksum.h
> +++ b/arch/arm64/include/asm/checksum.h
> @@ -25,6 +25,9 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
>  	__uint128_t tmp;
>  	u64 sum;
>  
> +	if (unlikely(ihl < 5))
> +		return 1;
> +
>  	tmp = *(const __uint128_t *)iph;
>  	iph += 16;
>  	ihl -= 4;

IHL in IPv4 should be at least 5. Do you have a stack trace to show how
it got here? Maybe the caller should ensure that the correct size is
passed.

Thanks.

-- 
Catalin

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