CVE-2022-49990

01/Description

In the Linux kernel, the following vulnerability has been resolved: s390: fix double free of GS and RI CBs on fork() failure The pointers for guarded storage and runtime instrumentation control blocks are stored in the thread_struct of the associated task. These pointers are initially copied on fork() via arch_dup_task_struct() and then cleared via copy_thread() before fork() returns. If fork() happens to fail after the initial task dup and before copy_thread(), the newly allocated task and associated thread_struct memory are freed via free_task() -> arch_release_task_struct(). This results in a double free of the guarded storage and runtime info structs because the fields in the failed task still refer to memory associated with the source task. This problem can manifest as a BUG_ON() in set_freepointer() (with CONFIG_SLAB_FREELIST_HARDENED enabled) or KASAN splat (if enabled) when running trinity syscall fuzz tests on s390x. To avoid this problem, clear the associated pointer fields in arch_dup_task_struct() immediately after the new task is copied. Note that the RI flag is still cleared in copy_thread() because it resides in thread stack memory and that is where stack info is copied.

02/Affected products

linux: linux kernel

03/References6

• git.kernel.org/stable/c/13cccafe0edcd03bf1c841de8ab8a1c8e34f77d9 Patch
• git.kernel.org/stable/c/25a95303b9e513cd2978aacc385d06e6fec23d07 Patch
• git.kernel.org/stable/c/297ae7e87a87a001dd3dfeac1cb26a42fd929708 Patch
• git.kernel.org/stable/c/8195e065abf3df84eb0ad2987e76a40f21d1791c Patch
• git.kernel.org/stable/c/cacd522e6652fbc2dc0cc6ae11c4e30782fef14b Patch
• git.kernel.org/stable/c/fbdc482d43eda40a70de4b0155843d5472f6de62 Patch