Messages in this thread | | | From | Tobias Waldekranz <> | Subject | Re: [RFC PATCH] net: phy/mdio: enable mmd indirect access through phy_mii_ioctl() | Date | Thu, 04 Nov 2021 14:13:08 +0100 |
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On Thu, Nov 04, 2021 at 12:40, "Russell King (Oracle)" <linux@armlinux.org.uk> wrote: > On Thu, Nov 04, 2021 at 12:35:17PM +0000, Russell King (Oracle) wrote: >> On Thu, Nov 04, 2021 at 12:17:47PM +0100, Tobias Waldekranz wrote: >> > Except that there is a way: https://github.com/wkz/mdio-tools >> >> I'm guessing that this hasn't had much in the way of review, as it has >> a nice exploitable bug - you really want "pc" to be unsigned in >> mdio_nl_eval(), otherwise one can write a branch instruction that makes >> "pc" negative. >> >> Also it looks like one can easily exploit this to trigger any of your >> BUG_ON()/BUG() statements, thereby crashing while holding the MDIO bus >> lock causing a denial of service attack. >> >> I also see nothing that protects against any user on a system being >> able to use this interface, so the exploits above can be triggered by >> any user. Moreover, this lack of protection means any user on the >> system can use this interface to write to a PHY. >> >> Given that some PHYs today contain firmware, this gives anyone access >> to reprogram the PHY firmware, possibly introducing malicious firmware. >> >> I hope no one is using this module in a production environment. > > It also leaks the reference count on the MDIO bus class device. > mdio_find_bus(), rather class_find_device_by_name() takes a reference > on the struct device that you never drop. See the documentation for > class_find_device() for the statement about this: > > * Note, you will need to drop the reference with put_device() after use.
Ahh interesting. Thanks!
> Of course, mdio_find_bus() documentation should _really_ have mentioned > this fact too.
Yeah, that would have been helpful.
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