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    Subject[PATCH] phy: mdio: fix memory leak
    Date
    Syzbot reported memory leak in MDIO bus interface, the problem was in
    wrong state logic.

    MDIOBUS_ALLOCATED indicates 2 states:
    1. Bus is only allocated
    2. Bus allocated and __mdiobus_register() fails, but
    device_register() was called

    In case of device_register() has been called we should call put_device()
    to correctly free the memory allocated for this device, but mdiobus_free()
    was just calling kfree(dev) in case of MDIOBUS_ALLOCATED state

    To avoid this behaviour we can add new intermediate state, which means,
    that we have called device_regiter(), but failed on any of the next steps.
    Clean up process for this state is the same as for MDIOBUS_UNREGISTERED,
    but MDIOBUS_UNREGISTERED name does not fit to the logic described above.

    Fixes: 46abc02175b3 ("phylib: give mdio buses a device tree presence")
    Reported-and-tested-by: syzbot+398e7dc692ddbbb4cfec@syzkaller.appspotmail.com
    Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
    ---
    drivers/net/phy/mdio_bus.c | 4 +++-
    include/linux/phy.h | 1 +
    2 files changed, 4 insertions(+), 1 deletion(-)

    diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
    index 53f034fc2ef7..ed764638b449 100644
    --- a/drivers/net/phy/mdio_bus.c
    +++ b/drivers/net/phy/mdio_bus.c
    @@ -540,6 +540,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
    return -EINVAL;
    }

    + bus->state = MDIOBUS_DEV_REGISTERED;
    +
    mutex_init(&bus->mdio_lock);
    mutex_init(&bus->shared_lock);

    @@ -647,7 +649,7 @@ void mdiobus_free(struct mii_bus *bus)
    return;
    }

    - BUG_ON(bus->state != MDIOBUS_UNREGISTERED);
    + BUG_ON(bus->state != MDIOBUS_UNREGISTERED && bus->state != MDIOBUS_DEV_REGISTERED);
    bus->state = MDIOBUS_RELEASED;

    put_device(&bus->dev);
    diff --git a/include/linux/phy.h b/include/linux/phy.h
    index 736e1d1a47c4..41d2ccdacd5e 100644
    --- a/include/linux/phy.h
    +++ b/include/linux/phy.h
    @@ -343,6 +343,7 @@ struct mii_bus {
    MDIOBUS_REGISTERED,
    MDIOBUS_UNREGISTERED,
    MDIOBUS_RELEASED,
    + MDIOBUS_DEV_REGISTERED,
    } state;

    /** @dev: Kernel device representation */
    --
    2.33.0
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