netdev - Re: [PATCH net v2] r6040: Fix kmemleak in probe and remove

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Date:   Wed, 14 Dec 2022 09:14:31 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Li Zetao <lizetao1@...wei.com>
Cc:     weiyongjun1@...wei.com, davem@...emloft.net, edumazet@...gle.com,
        f.fainelli@...il.com, kuba@...nel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        pabeni@...hat.com
Subject: Re: [PATCH net v2] r6040: Fix kmemleak in probe and remove

On Tue, Dec 13, 2022 at 08:56:14PM +0800, Li Zetao wrote:
> There is a memory leaks reported by kmemleak:
> 
>   unreferenced object 0xffff888116111000 (size 2048):
>     comm "modprobe", pid 817, jiffies 4294759745 (age 76.502s)
>     hex dump (first 32 bytes):
>       00 c4 0a 04 81 88 ff ff 08 10 11 16 81 88 ff ff  ................
>       08 10 11 16 81 88 ff ff 00 00 00 00 00 00 00 00  ................
>     backtrace:
>       [<ffffffff815bcd82>] kmalloc_trace+0x22/0x60
>       [<ffffffff827e20ee>] phy_device_create+0x4e/0x90
>       [<ffffffff827e6072>] get_phy_device+0xd2/0x220
>       [<ffffffff827e7844>] mdiobus_scan+0xa4/0x2e0
>       [<ffffffff827e8be2>] __mdiobus_register+0x482/0x8b0
>       [<ffffffffa01f5d24>] r6040_init_one+0x714/0xd2c [r6040]
>       ...
> 
> The problem occurs in probe process as follows:
>   r6040_init_one:
>     mdiobus_register
>       mdiobus_scan    <- alloc and register phy_device,
>                          the reference count of phy_device is 3
>     r6040_mii_probe
>       phy_connect     <- connect to the first phy_device,
>                          so the reference count of the first
>                          phy_device is 4, others are 3
>     register_netdev   <- fault inject succeeded, goto error handling path
> 
>     // error handling path
>     err_out_mdio_unregister:
>       mdiobus_unregister(lp->mii_bus);
>     err_out_mdio:
>       mdiobus_free(lp->mii_bus);    <- the reference count of the first
>                                        phy_device is 1, it is not released
>                                        and other phy_devices are released
>   // similarly, the remove process also has the same problem
> 
> The root cause is traced to the phy_device is not disconnected when
> removes one r6040 device in r6040_remove_one() or on error handling path
> after r6040_mii probed successfully. In r6040_mii_probe(), a net ethernet
> device is connected to the first PHY device of mii_bus, in order to
> notify the connected driver when the link status changes, which is the
> default behavior of the PHY infrastructure to handle everything.
> Therefore the phy_device should be disconnected when removes one r6040
> device or on error handling path.
> 
> Fix it by adding phy_disconnect() when removes one r6040 device or on
> error handling path after r6040_mii probed successfully.
> 
> Fixes: 3831861b4ad8 ("r6040: implement phylib")
> Signed-off-by: Li Zetao <lizetao1@...wei.com>
> ---
> v1 -> v2: change the subject prefix "PATCH" to "PATCH net" and change
> the goto label name "err_out_r6040_mii_remove" to "err_out_phy_disconnect"
> 
>  drivers/net/ethernet/rdc/r6040.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 

Please don't send new patches as reply-to.

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>