linux-kernel - Re: [PATCH v2] net: phy: Fix use after free in phy

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Message-Id: <20161129.203540.1821619500745777807.davem@davemloft.net>
Date:   Tue, 29 Nov 2016 20:35:40 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     geert+renesas@...der.be
Cc:     f.fainelli@...il.com, josh.cartwright@...com,
        nathan.sullivan@...com, zach.brown@...com,
        woojung.huh@...rochip.com, netdev@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: phy: Fix use after free in phy_detach()

From: Geert Uytterhoeven <geert+renesas@...der.be>
Date: Mon, 28 Nov 2016 15:18:31 +0100

> If device_release_driver(&phydev->mdio.dev) is called, it releases all
> resources belonging to the PHY device. Hence the subsequent call to
> phy_led_triggers_unregister() will access already freed memory when
> unregistering the LEDs.
> 
> Move the call to phy_led_triggers_unregister() before the possible call
> to device_release_driver() to fix this.
> 
> Fixes: 2e0bc452f4721520 ("net: phy: leds: add support for led triggers on phy link state change")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> This is v2 of "[RFC] net: phy: Fix double free in phy_detach()".
> 
> v2:
>   - Dropped RFC,
>   - Reworded, as commit a7dac9f9c1695d74 ("phy: fix error case of
>     phy_led_triggers_(un)register") fixed the double free, and thus the
>     warning I was seeing during "poweroff" on sh73a0/kzm9g,
>   - Verified use after free using CONFIG_DEBUG_DEVRES, log_devres = 1,
>     and additional debug code printing the address of
>     phy->phy_led_triggers. Adding poisoning of freed memory to
>     devres_log() will cause a crash.

Applied, thanks.