[PATCH] drivers/i2c-aspeed: avoid invalid memory reference after timeout

[Heyi Guo]

The memory will be freed by the caller if transfer timeout occurs,
then it would trigger kernel panic if the peer device responds with
something after timeout and triggers the interrupt handler of aspeed
i2c driver.

Set the msgs pointer to NULL to avoid invalid memory reference after
timeout to fix this potential kernel panic.

Signed-off-by: Heyi Guo <guoheyi at linux.alibaba.com>

-------

Cc: Brendan Higgins <brendanhiggins at google.com>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Joel Stanley <joel at jms.id.au>
Cc: Andrew Jeffery <andrew at aj.id.au>
Cc: Philipp Zabel <p.zabel at pengutronix.de>
Cc: linux-i2c at vger.kernel.org
Cc: openbmc at lists.ozlabs.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-aspeed at lists.ozlabs.org
---
 drivers/i2c/busses/i2c-aspeed.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 67e8b97c0c950..3ab0396168680 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -708,6 +708,11 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
 		spin_lock_irqsave(&bus->lock, flags);
 		if (bus->master_state == ASPEED_I2C_MASTER_PENDING)
 			bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
+		/*
+		 * All the buffers may be freed after returning to caller, so
+		 * set msgs to NULL to avoid memory reference after freeing.
+		 */
+		bus->msgs = NULL;
 		spin_unlock_irqrestore(&bus->lock, flags);
 
 		return -ETIMEDOUT;
-- 
2.17.1