CVE-2025-38100

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

x86/iopl: Cure TIF_IO_BITMAP inconsistencies

io_bitmap_exit() is invoked from exit_thread() when a task exists or

when a fork fails. In the latter case the exit_thread() cleans up

resources which were allocated during fork().

io_bitmap_exit() invokes task_update_io_bitmap(), which in turn ends up

in tss_update_io_bitmap(). tss_update_io_bitmap() operates on the

current task. If current has TIF_IO_BITMAP set, but no bitmap installed,

tss_update_io_bitmap() crashes with a NULL pointer dereference.

There are two issues, which lead to that problem:

1) io_bitmap_exit() should not invoke task_update_io_bitmap() when

the task, which is cleaned up, is not the current task. That's a

clear indicator for a cleanup after a failed fork().

2) A task should not have TIF_IO_BITMAP set and neither a bitmap

installed nor IOPL emulation level 3 activated.

This happens when a kernel thread is created in the

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References