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

KVM: x86: Check for invalid/obsolete root after making MMU pages available

Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages.

Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages.

Note #2, inheriting role.invalid when creating child shadow pages is also far from ideal; that flaw will be addressed separately.

KVM: x86: Check for invalid/obsolete root *after* making MMU pages available

Red Hat Security Advisory: kernel security update

Important

A flaw was found in the Linux kernel’s filesystem notification (fs/notify) code where calling inotify_show_fdinfo() on a file descriptor watching an overlayfs inode during an unmount operation could lead to a NULL pointer dereference.

CWE-476 - NULL Pointer Dereference

Race condition vulnerabilities were found in the Linux kernel's SCSI error handler wake-up logic. Memory ordering issues in scsi_dec_host_busy() and ordering problems in scsi_eh_inc_host_failed() can cause the SCSI error handler to never wake up when command completions race against each other. This leaves I/O stuck indefinitely as the error recovery state cannot advance.

CWE-821 - Incorrect Synchronization

A flaw was found in the Linux kernel's rtnetlink component. An unprivileged local user, leveraging a user namespace, can exploit a missing `CAP_NET_ADMIN` capability check in the `rtnl_newlink()` function. This allows the user to create paired network devices in arbitrary network namespaces, including the `init_net` (initial network namespace). Such unauthorized creation of network interfaces could lead to unexpected network configurations and potential system instability or resource exhaustion.

CWE-272 - Least Privilege Violation