CVE-2025-38535: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-38535 affects the Linux kernel and involves an issue with the UTMI PHY mode in the Tegra XUSB padctl driver. The vulnerability was discovered when transitioning from USBROLEDEVICE to USBROLENONE, where incorrect handling of regulator disable operations could occur (Debian Tracker).

The vulnerability occurs in the phy: tegra: xusb component when the code assumes that a regulator should be disabled during role transitions. When the regulator is marked as always-on, regulatorisenabled() continues to return true, leading to an incorrect attempt to disable a regulator which is not enabled. This results in unbalanced regulator disable operations, causing system warnings (Debian Tracker).

The vulnerability can result in system warnings and improper regulator state management. For example, it can trigger warnings such as 'WARNING: CPU: 1 PID: 7326 at drivers/regulator/core.c:3004 regulatordisable+0xe4/0x1a0' and 'unbalanced disables for VINSYS5V0' (Debian Tracker).

The fix involves moving the regulator control logic into the tegra186xusbpadctlidoverride() function since it's directly related to the ID override state. The regulator is now only disabled when the role transitions from USBROLEHOST to USBROLENONE, by checking the VBUS_ID register. This ensures that regulator enable/disable operations are properly balanced and only occur when actually transitioning to/from host mode. The fix has been implemented in Linux kernel version 6.1.147-1 for Debian bookworm and 6.12.41-1 for Debian trixie (Debian Tracker).