OESA-2023-1157

The Linux Kernel, the operating system core itself.

Security Fix(es):

There is a logic error in iouring's implementation which can be used to trigger a use-after-free vulnerability leading to privilege escalation. In the ioprepasyncwork function the assumption that the last iograbidentity 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 VIDIOCSDV_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/specctrl.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 ibprctlset [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 SPECCTRL MSR on the function _speculationctrl_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 iouring subsystem, it is possible to leak kernel memory information to the user process. timensinstall calls currentissinglethreaded to determine if the current process is single-threaded, but this call does not consider iouring's ioworker 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/iouring(CVE-2023-23586)