[SRU][N][PATCH 1/1] i2c: smbus: fix NULL function pointer dereference

[Bethany Jamison]

From: Wolfram Sang <wsa+renesas at sang-engineering.com>

[ Upstream commit 91811a31b68d3765b3065f4bb6d7d6d84a7cfc9f ]

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 at 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 at sang-engineering.com>
Tested-by: Baruch Siach <baruch at tkos.co.il>
Signed-off-by: Sasha Levin <sashal at kernel.org>
(cherry picked from commit 357c64ef1ef39b1e7cd91ab6bdd304d043702c83 linux-6.8.y)
CVE-2024-35984
Signed-off-by: Bethany Jamison <bethany.jamison at canonical.com>
---
 drivers/i2c/i2c-core-base.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 3bd48d4b6318f..5e2cefb37e1a4 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,
-- 
2.34.1