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Re: [PATCH 6/6] hw/i2c: Implement NPCM7XX SMBus Module FIFO Mode


From: Corey Minyard
Subject: Re: [PATCH 6/6] hw/i2c: Implement NPCM7XX SMBus Module FIFO Mode
Date: Tue, 26 Jan 2021 17:47:24 -0600

On Tue, Jan 26, 2021 at 11:32:37AM -0800, wuhaotsh--- via wrote:
> +
> +static void npcm7xx_smbus_read_byte_fifo(NPCM7xxSMBusState *s)
> +{
> +    uint8_t received_bytes = NPCM7XX_SMBRXF_STS_RX_BYTES(s->rxf_sts);
> +
> +    if (received_bytes == 0) {
> +        npcm7xx_smbus_recv_fifo(s);
> +        return;
> +    }
> +
> +    s->sda = s->rx_fifo[s->rx_cur];
> +    s->rx_cur = (s->rx_cur + 1u) % NPCM7XX_SMBUS_FIFO_SIZE;
> +    --s->rxf_sts;

This open-coded decrement seems a little risky.  Are you sure in every
case that s->rxf_sts > 0?  There's no way what's running in the VM can
game this and cause a buffer overrun?  One caller to this function seems
to protect against this, and another does not.

Other than this, I didn't see any issues with this patch.

-corey



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