On Tue, Jan 07, 2025 at 04:51:29PM +0800, Ma Ke wrote:
The reference count of the device incremented in device_initialize() is not decremented properly when device_add() fails. Change device_unregister() to a put_device() call before returning from the function to decrement reference count for cleanup. Or it could cause memory leak.
As comment of device_add() says, 'if device_add() succeeds, you should call device_del() when you want to get rid of it. If device_add() has not succeeded, use only put_device() to drop the reference count'.
Found by code review.
While the patch looks correct, the commit message seems confusing to me.
device_unregister() will also call put_device() after first calling device_del(). So the reference count /is/ properly balanced.
Instead, the kerneldoc comment for device_add() says this:
* NOTE: _Never_ directly free @dev after calling this function, even * if it returned an error! Always use put_device() to give up your * reference instead. * * Rule of thumb is: if device_add() succeeds, you should call * device_del() when you want to get rid of it. If device_add() has * *not* succeeded, use *only* put_device() to drop the reference * count.
So the real reason that this patch is correct is because device_unregister() should only be called after device_add() succeeded because device_del() undoes what device_add() does if successful. In this case we only need to undo what device_initialize() does, and that is what put_device() will do.
Thierry
Cc: stable@vger.kernel.org Fixes: 53d2a715c240 ("phy: Add Tegra XUSB pad controller support") Signed-off-by: Ma Ke make24@iscas.ac.cn
drivers/phy/tegra/xusb.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/phy/tegra/xusb.c b/drivers/phy/tegra/xusb.c index 79d4814d758d..c89df95aa6ca 100644 --- a/drivers/phy/tegra/xusb.c +++ b/drivers/phy/tegra/xusb.c @@ -548,16 +548,16 @@ static int tegra_xusb_port_init(struct tegra_xusb_port *port, err = dev_set_name(&port->dev, "%s-%u", name, index); if (err < 0)
goto unregister;
goto put_device;err = device_add(&port->dev); if (err < 0)
goto unregister;
goto put_device;return 0; -unregister:
- device_unregister(&port->dev);
+put_device:
- put_device(&port->dev); return err;
} -- 2.25.1