[PATCH v2 1/6] i2c: xiic: Fix broken locking on tx_msg

Marek Vasut
2021-08-23T21:42:19Z

The tx_msg is set from multiple places, sometimes without locking,
which fall apart on any SMP system. Only ever access tx_msg inside
the driver mutex.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Cc: Wolfram Sang <wsa@kernel.org>
---
V2: Initialize RX message pointer in xiic_start_xfer() too
---
drivers/i2c/busses/i2c-xiic.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index bb93db98404ef..50320dd32eea9 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -170,7 +170,7 @@ struct xiic_i2c {
#define xiic_tx_space(i2c) ((i2c)->tx_msg->len - (i2c)->tx_pos)
#define xiic_rx_space(i2c) ((i2c)->rx_msg->len - (i2c)->rx_pos)

-static int xiic_start_xfer(struct xiic_i2c *i2c);
+static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num);
static void __xiic_start_xfer(struct xiic_i2c *i2c);

/*
@@ -684,15 +684,25 @@ static void __xiic_start_xfer(struct xiic_i2c *i2c)

}

-static int xiic_start_xfer(struct xiic_i2c *i2c)
+static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
{
int ret;
+
mutex_lock(&i2c->lock);

+ ret = xiic_busy(i2c);
+ if (ret)
+ goto out;
+
+ i2c->tx_msg = msgs;
+ i2c->rx_msg = NULL;
+ i2c->nmsgs = num;
+
ret = xiic_reinit(i2c);
if (!ret)
__xiic_start_xfer(i2c);

+out:
mutex_unlock(&i2c->lock);

return ret;
@@ -710,14 +720,7 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
if (err < 0)
return err;

- err = xiic_busy(i2c);
- if (err)
- goto out;
-
- i2c->tx_msg = msgs;
- i2c->nmsgs = num;
-
- err = xiic_start_xfer(i2c);
+ err = xiic_start_xfer(i2c, msgs, num);
if (err < 0) {
dev_err(adap->dev.parent, "Error xiic_start_xfer\n");
goto out;
@@ -725,9 +728,11 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)

if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
(i2c->state == STATE_DONE), HZ)) {
+ mutex_lock(&i2c->lock);
err = (i2c->state == STATE_DONE) ? num : -EIO;
goto out;
} else {
+ mutex_lock(&i2c->lock);
i2c->tx_msg = NULL;
i2c->rx_msg = NULL;
i2c->nmsgs = 0;
@@ -735,6 +740,7 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
goto out;
}
out:
+ mutex_unlock(&i2c->lock);
pm_runtime_mark_last_busy(i2c->dev);
pm_runtime_put_autosuspend(i2c->dev);
return err;
--
2.32.0