serial: mxs-auart: Fix potential infinite loop

[ Upstream commit 5963e8a3122471cadfe0eba41c4ceaeaa5c8bb4d ]

On the error path of mxs_auart_request_gpio_irq() is performed
backward iterating with index i of enum type. Underline enum type
may be unsigned char. In this case check (--i >= 0) will be always
true and error handling goes into infinite loop.

The patch changes the check so that it is valid for signed and unsigned
types.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Anton Vasilyev <vasilyev@ispras.ru>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 1d9d778828baed6c15e3837b6a6a03a0ad4d5d6c..515bf18c829434d9a8cd635e5577544fe884f4c4 100644 (file)
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -1635,8 +1635,9 @@ static int mxs_auart_request_gpio_irq(struct mxs_auart_port *s)
 
        /*
         * If something went wrong, rollback.
+        * Be careful: i may be unsigned.
         */
-       while (err && (--i >= 0))
+       while (err && (i-- > 0))
                if (irq[i] >= 0)
                        free_irq(irq[i], s);