linux-kernel - Re: [PATCH v2] nvmem: meson-mx-efuse: allow reading data smaller than word

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Date:   Mon, 29 Jul 2019 15:04:27 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org, srinivas.kandagatla@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] nvmem: meson-mx-efuse: allow reading data smaller than
 word_size

On 27/07/2019 21:34, Martin Blumenstingl wrote:
> Some Amlogic boards store the Ethernet MAC address inside the eFuse. The
> Ethernet MAC address uses 6 bytes. The existing logic in
> meson_mx_efuse_read() would write beyond the end of the data buffer when
> trying to read data with a size that is not aligned to word_size (4
> bytes on Meson8, Meson8b and Meson8m2).
> 
> Calculate the remaining data to copy inside meson_mx_efuse_read() so
> reading 6 bytes doesn't write beyond the end of the data buffer.
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
> Changes since v1:
> - switch from min() to min_t() to get rid of a compiler warning
> 
> 
>  drivers/nvmem/meson-mx-efuse.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvmem/meson-mx-efuse.c b/drivers/nvmem/meson-mx-efuse.c
> index 2976aef87c82..e8fc0baa09e7 100644
> --- a/drivers/nvmem/meson-mx-efuse.c
> +++ b/drivers/nvmem/meson-mx-efuse.c
> @@ -155,7 +155,8 @@ static int meson_mx_efuse_read(void *context, unsigned int offset,
>  		if (err)
>  			break;
>  
> -		memcpy(buf + i, &tmp, efuse->config.word_size);
> +		memcpy(buf + i, &tmp,
> +		       min_t(size_t, bytes - i, efuse->config.word_size));
>  	}
>  
>  	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
> 

Reviewed-by: Neil Armstrong <narmstrong@...libre.com>