linux-kernel - [PATCH v2] serial: 8250_core: actually limit char reads to max

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Message-ID: <1415304617-14835-1-git-send-email-frans.klaver@xsens.com>
Date:	Thu, 6 Nov 2014 21:10:17 +0100
From:	Frans Klaver <frans.klaver@...ns.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Frans Klaver <frans.klaver@...ns.com>, Jiri Slaby <jslaby@...e.cz>,
	<linux-serial@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] serial: 8250_core: actually limit char reads to max_count

In serial8250_rx_chars(), max_count is set to 256. Due to the
post-decrement operator used in the while() condition, the maximum
number of iterations actually 257. This is not a problem, but it is
mildly surprising if you're debugging. Use pre-decrement instead.

Signed-off-by: Frans Klaver <frans.klaver@...ns.com>
---
v1..v2: change subject to better reflect the goal of the patch

 drivers/tty/serial/8250/8250_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index a06084d..cc9f1a8 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1485,7 +1485,7 @@ serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
 
 ignore_char:
 		lsr = serial_in(up, UART_LSR);
-	} while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (max_count-- > 0));
+	} while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (--max_count > 0));
 	spin_unlock(&port->lock);
 	tty_flip_buffer_push(&port->state->port);
 	spin_lock(&port->lock);
-- 
2.1.0

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