CVE-2025-40120

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> net: usb: asix: hold PM usage ref to avoid PM/MDIO + RTNL deadlock<br /> <br /> Prevent USB runtime PM (autosuspend) for AX88772* in bind.<br /> <br /> usbnet enables runtime PM (autosuspend) by default, so disabling it via<br /> the usb_driver flag is ineffective. On AX88772B, autosuspend shows no<br /> measurable power saving with current driver (no link partner, admin<br /> up/down). The ~0.453 W -&gt; ~0.248 W drop on v6.1 comes from phylib powering<br /> the PHY off on admin-down, not from USB autosuspend.<br /> <br /> The real hazard is that with runtime PM enabled, ndo_open() (under RTNL)<br /> may synchronously trigger autoresume (usb_autopm_get_interface()) into<br /> asix_resume() while the USB PM lock is held. Resume paths then invoke<br /> phylink/phylib and MDIO, which also expect RTNL, leading to possible<br /> deadlocks or PM lock vs MDIO wake issues.<br /> <br /> To avoid this, keep the device runtime-PM active by taking a usage<br /> reference in ax88772_bind() and dropping it in unbind(). A non-zero PM<br /> usage count blocks runtime suspend regardless of userspace policy<br /> (.../power/control - pm_runtime_allow/forbid), making this approach<br /> robust against sysfs overrides.<br /> <br /> Holding a runtime-PM usage ref does not affect system-wide suspend;<br /> system sleep/resume callbacks continue to run as before.