linux-kernel - [PATCH v2] serial: 8250_pci1xxxx: fix off by one in pci1xxxx_process_read

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Date: Wed, 10 Jan 2024 22:25:21 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Rengarajan S <rengarajan.s@...rochip.com>
Cc: Kumaravel Thiagarajan <kumaravel.thiagarajan@...rochip.com>,
	Tharun Kumar P <tharunkumar.pasumarthi@...rochip.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH v2] serial: 8250_pci1xxxx: fix off by one in
 pci1xxxx_process_read_data()

These > comparisons should be >= to prevent writing one element beyond
the end of the rx_buff[] array.  The rx_buff[] buffer has RX_BUF_SIZE
elements.  Fix the buffer overflow.

Fixes: aba8290f368d ("8250: microchip: pci1xxxx: Add Burst mode reception support in uart driver for writing into FIFO")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
v2: Add "fix" to the subject.  Fix a typo in the commit message as well.

 drivers/tty/serial/8250/8250_pci1xxxx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_pci1xxxx.c b/drivers/tty/serial/8250/8250_pci1xxxx.c
index 558c4c7f3104..cd258922bd78 100644
--- a/drivers/tty/serial/8250/8250_pci1xxxx.c
+++ b/drivers/tty/serial/8250/8250_pci1xxxx.c
@@ -302,7 +302,7 @@ static void pci1xxxx_process_read_data(struct uart_port *port,
 	 * to read, the data is received one byte at a time.
 	 */
 	while (valid_burst_count--) {
-		if (*buff_index > (RX_BUF_SIZE - UART_BURST_SIZE))
+		if (*buff_index >= (RX_BUF_SIZE - UART_BURST_SIZE))
 			break;
 		burst_buf = (u32 *)&rx_buff[*buff_index];
 		*burst_buf = readl(port->membase + UART_RX_BURST_FIFO);
@@ -311,7 +311,7 @@ static void pci1xxxx_process_read_data(struct uart_port *port,
 	}
 
 	while (*valid_byte_count) {
-		if (*buff_index > RX_BUF_SIZE)
+		if (*buff_index >= RX_BUF_SIZE)
 			break;
 		rx_buff[*buff_index] = readb(port->membase +
 					     UART_RX_BYTE_FIFO);
-- 
2.43.0