[PATCH] i2c: smbus: fix NULL function pointer dereference

Wolfram Sang
2024-04-26T06:44:28Z

Brauch reported an OOPS when using the designware controller as target
only. Target-only modes break the assumption of one transfer function
always being available. Fix this by always checking the pointer in
__i2c_transfer.

Reported-by: Baruch Siach <baruch@tkos.co.il>
Closes: https://lore.kernel.org/r/4269631780e5ba789cf1ae391eec1b959def7d99.1712761976.git.baruch@tkos.co.il
Fixes: 4b1acc43331d ("i2c: core changes for slave support")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
drivers/i2c/i2c-core-base.c | 12 ++++++------
drivers/i2c/i2c-core-smbus.c | 2 +-
2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index ff5c486a1dbb..db0d1ac82910 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2200,13 +2200,18 @@ static int i2c_check_for_quirks(struct i2c_adapter *adap, struct i2c_msg *msgs,
* Returns negative errno, else the number of messages executed.
*
* Adapter lock must be held when calling this function. No debug logging
- * takes place. adap->algo->master_xfer existence isn't checked.
+ * takes place.
*/
int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
unsigned long orig_jiffies;
int ret, try;

+ if (!adap->algo->master_xfer) {
+ dev_dbg(&adap->dev, "I2C level transfers not supported\n");
+ return -EOPNOTSUPP;
+ }
+
if (WARN_ON(!msgs || num < 1))
return -EINVAL;

@@ -2273,11 +2278,6 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
int ret;

- if (!adap->algo->master_xfer) {
- dev_dbg(&adap->dev, "I2C level transfers not supported\n");
- return -EOPNOTSUPP;
- }
-
/* REVISIT the fault reporting model here is weak:
*
* - When we get an error after receiving N bytes from a slave,
diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index e3b96fc53b5c..a942c5306a4e 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -596,7 +596,7 @@ s32 __i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
break;
}

- if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
+ if (res != -EOPNOTSUPP)
goto trace;
/*
* Fall back to i2c_smbus_xfer_emulated if the adapter doesn't
--
2.39.2