Affected: Linux

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.

kernel: fs/notify: call exportfs_encode_fid with s_umount kernel: scsi: core: Wake up the error handler when final completions race against each other kernel: rtnetlink: add missing netlink_ns_capable() check for peer netns kernel: net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels kernel: futex: Drop CLONE_THREAD requirement for private default hash alloc kernel: dm log: fix out-of-bounds write due to region_count overflow kernel: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available

kernel: KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O kernel: tipc: fix double-free in tipc_buf_append() kernel: dm log: fix out-of-bounds write due to region_count overflow kernel: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available