CVE-2022-49990: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-49990 affects the Linux kernel and involves a double free vulnerability in the s390 architecture's handling of guarded storage and runtime instrumentation control blocks during fork() failure. The vulnerability was disclosed on June 18, 2025 (NVD).

The vulnerability occurs when fork() fails after the initial task duplication but before copythread() execution. The pointers for guarded storage and runtime instrumentation control blocks are stored in the threadstruct of the associated task. These pointers are initially copied via archduptaskstruct() and then cleared via copythread(). If failure occurs between these operations, the newly allocated task and associated threadstruct memory are freed via freetask() -> archreleasetask_struct(), resulting in a double free condition (NVD).

This vulnerability can manifest as a BUGON() in setfreepointer() when CONFIGSLABFREELIST_HARDENED is enabled, or as a KASAN splat if enabled, particularly when running trinity syscall fuzz tests on s390x systems (NVD).

The issue has been resolved by clearing the associated pointer fields in archduptaskstruct() immediately after the new task is copied. The RI flag is still cleared in copythread() as it resides in thread stack memory where stack information is copied (NVD).