[PATCH 6/8] i2c: core: fix adapter deregistration race

[Johan Hovold <johan@kernel.org>]

Adapters can be looked up by their id using i2c_get_adapter() which
takes a reference to the embedded struct device.

Remove the adapter from the IDR before tearing it down during
deregistration to make sure its resources are not accessed after having
been freed (e.g. the device name).

Fixes: 35fc37f81881 ("i2c: Limit core locking to the necessary sections")
Cc: stable@vger.kernel.org	# 2.6.31
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/i2c/i2c-core-base.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index be909d6bc776..6209c5587e99 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1799,6 +1799,8 @@ void i2c_del_adapter(struct i2c_adapter *adap)
 	/* First make sure that this adapter was ever added */
 	mutex_lock(&core_lock);
 	found = idr_find(&i2c_adapter_idr, adap->nr);
+	if (found == adap)
+		idr_replace(&i2c_adapter_idr, NULL, adap->nr);
 	mutex_unlock(&core_lock);
 	if (found != adap) {
 		pr_debug("attempting to delete unregistered adapter [%s]\n", adap->name);
-- 
2.53.0