kernel security update
The Linux Kernel, the operating system core itself.
Security Fix(es):
There is a logic error in io_uring's implementation which can be used to trigger a use-after-free vulnerability leading to privilege escalation. In the io_prep_async_work function the assumption that the last io_grab_identity call cannot return false is not true, and in this case the function will use the init_cred or the previous linked requests identity to do operations instead of using the current identity. This can lead to reference counting issues causing use-after-free. We recommend upgrading past version 5.10.161.(CVE-2023-0240)
A memory leak flaw and potential divide by zero and Integer overflow was found in the Linux kernel V4L2 and vivid test code functionality. This issue occurs when a user triggers ioctls, such as VIDIOC_S_DV_TIMINGS ioctl. This could allow a local user to crash the system if vivid test code enabled.(CVE-2023-0615)
The Linux kernel does not correctly mitigate SMT attacks, as discovered
through a strange pattern in the kernel API using STIBP as a mitigation[1
<https://docs.kernel.org/userspace-api/spec_ctrl.html>], leaving the
process exposed for a short period of time after a syscall. The kernel also
does not issue an IBPB immediately during the syscall.
The ib_prctl_set [2
<https://elixir.bootlin.com/linux/v5.15.56/source/arch/x86/kernel/cpu/bugs.c#L1467>]function
updates the Thread Information Flags (TIFs) for the task and updates the
SPEC_CTRL MSR on the function __speculation_ctrl_update [3
<https://elixir.bootlin.com/linux/v5.15.56/source/arch/x86/kernel/process.c#L557>],
but the IBPB is only issued on the next schedule, when the TIF bits are
checked. This leaves the victim vulnerable to values already injected on
the BTB, prior to the prctl syscall.
The behavior is only corrected after a reschedule of the task happens.
Furthermore, the kernel entrance (due to the syscall itself), does not
issue an IBPB in the default scenarios (i.e., when the kernel protects
itself via retpoline or eIBRS).(CVE-2023-0045)
Due to a vulnerability in the io_uring subsystem, it is possible to leak kernel memory information to the user process. timens_install calls current_is_single_threaded to determine if the current process is single-threaded, but this call does not consider io_uring's io_worker threads, thus it is possible to insert a time namespace's vvar page to process's memory space via a page fault. When this time namespace is destroyed, the vvar page is also freed, but not removed from the process' memory, and a next page allocated by the kernel will be still available from the user-space process and can leak memory contents via this (read-only) use-after-free vulnerability. We recommend upgrading past version 5.10.161 or commit 788d0824269bef539fe31a785b1517882eafed93 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/io_uring(CVE-2023-23586)
