i2c: smbus: fix NULL function pointer dereference

Baruch 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")
[wsa: dropped the simplification in core-smbus to avoid theoretical regressions]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Baruch Siach <baruch@tkos.co.il>

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index ff5c486a1dbb1fa4a17d0d3f74885a7e3a0a69ec..db0d1ac82910e558b8df2e4e7f1c1f6535a06eaf 100644 (file)
--- 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,