i2c: acpi: Fix adapter reference leak in i2c_acpi_new_device_by_fwnode()

i2c_acpi_new_device_by_fwnode() obtains an i2c_adapter through
i2c_acpi_find_adapter_by_handle(). That helper uses bus_find_device()
internally, so it returns the adapter with a reference held:

        adapter = i2c_verify_adapter(dev);
        if (!adapter)
                put_device(dev);

        return adapter;

The reference is only put on the failure path inside that helper. The
caller owns it otherwise. i2c_acpi_new_device_by_fwnode() never drops
it, neither on the -EPROBE_DEFER path nor after
i2c_new_client_device(), so every call leaks one reference on the
adapter and the adapter can never be released.

i2c_new_client_device() does not consume that reference. It registers
the new client with the adapter as its parent, and device_add() takes
its own reference on the parent, which device_del() releases when the
client goes away.  The reference obtained by the lookup is a separate
one and has to be dropped here.

i2c_acpi_notify() in the same file already does exactly this. It takes
the adapter from the same helper, registers the client through
i2c_acpi_register_device(), which calls i2c_new_client_device(), and
then puts the reference.

i2c_new_client_device() gives the client its own reference on the
adapter, so ours can be dropped unconditionally.

Found by code review.

Fixes: 605f8fc22442 ("i2c: core: Add new i2c_acpi_new_device helper function")
Signed-off-by: Ma Ke <make_ruc2021@163.com>
Cc: <stable@vger.kernel.org> # v4.12+
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://patch.msgid.link/20261012013421.3597430-1-make_ruc2021@163.com

0 files changed, 0 insertions, 0 deletions