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[91.79.162.197]) by smtp.googlemail.com with ESMTPSA id p27sm2119121lfh.8.2019.06.10.11.12.23 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Jun 2019 11:12:23 -0700 (PDT) Subject: Re: [PATCH V4 6/6] i2c: tegra: remove BUG, BUG_ON To: Bitan Biswas , Laxman Dewangan , Thierry Reding , Jonathan Hunter , linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Rosin , Wolfram Sang Cc: Shardar Mohammed , Sowjanya Komatineni , Mantravadi Karthik References: <1560186515-30797-1-git-send-email-bbiswas@nvidia.com> <1560186515-30797-6-git-send-email-bbiswas@nvidia.com> From: Dmitry Osipenko Message-ID: <06ab30b6-bf79-c628-0a04-d0307511a06f@gmail.com> Date: Mon, 10 Jun 2019 21:12:22 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <1560186515-30797-6-git-send-email-bbiswas@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 10.06.2019 20:08, Bitan Biswas пишет: > Remove redundant BUG_ON calls or replace with WARN_ON_ONCE > as needed. Remove BUG() and make Rx and Tx case handling > similar. > > Signed-off-by: Bitan Biswas > --- > drivers/i2c/busses/i2c-tegra.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) Looks that this is still not correct. What if it transfer-complete flag is set and buffer is full on RX? In this case the transfer will succeed while it was a failure. > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c > index 4dfb4c1..30619d6 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -515,7 +515,6 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) > * prevent overwriting past the end of buf > */ > if (rx_fifo_avail > 0 && buf_remaining > 0) { > - BUG_ON(buf_remaining > 3); Actually error should be returned here since out-of-bounds memory accesses must be avoided, hence: if (WARN_ON_ONCE(buf_remaining > 3)) return -EINVAL; > val = i2c_readl(i2c_dev, I2C_RX_FIFO); > val = cpu_to_le32(val); > memcpy(buf, &val, buf_remaining); > @@ -523,7 +522,6 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) > rx_fifo_avail--; > } > > - BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0); Better not to ignore this as well: if (WARN_ON_ONCE(rx_fifo_avail > 0 && buf_remaining > 0)) return -EINVAL; > i2c_dev->msg_buf_remaining = buf_remaining; > i2c_dev->msg_buf = buf; > > @@ -581,7 +579,6 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev) > * boundary and fault. > */ > if (tx_fifo_avail > 0 && buf_remaining > 0) { > - BUG_ON(buf_remaining > 3); And here, cause this will corrupt stack: if (WARN_ON_ONCE(buf_remaining > 3)) return -EINVAL; > memcpy(&val, buf, buf_remaining); > val = le32_to_cpu(val); > > @@ -850,7 +847,8 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) > if (i2c_dev->msg_buf_remaining) > tegra_i2c_empty_rx_fifo(i2c_dev); > else > - BUG(); > + tegra_i2c_mask_irq(i2c_dev, > + I2C_INT_RX_FIFO_DATA_REQ); Then here: if (WARN_ON_ONCE(!i2c_dev->msg_buf_remaining) || tegra_i2c_empty_rx_fifo(i2c_dev)) { i2c_dev->msg_err |= I2C_ERR_UNKNOWN_INTERRUPT; goto err; } > } > > if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) { > @@ -876,7 +874,10 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) > if (status & I2C_INT_PACKET_XFER_COMPLETE) { > if (i2c_dev->is_curr_dma_xfer) > i2c_dev->msg_buf_remaining = 0; > - BUG_ON(i2c_dev->msg_buf_remaining); > + if (WARN_ON_ONCE(i2c_dev->msg_buf_remaining)) { > + i2c_dev->msg_err |= I2C_ERR_UNKNOWN_INTERRUPT; > + goto err; > + } > complete(&i2c_dev->msg_complete); > } > goto done; >