CVE-2021-47217

/// Technical description

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

x86/hyperv: Fix NULL deref in set_hv_tscchange_cb() if Hyper-V setup fails

Check for a valid hv_vp_index array prior to derefencing hv_vp_index when

setting Hyper-V's TSC change callback. If Hyper-V setup failed in

hyperv_init(), the kernel will still report that it's running under

Hyper-V, but will have silently disabled nearly all functionality.

BUG: kernel NULL pointer dereference, address: 0000000000000010

#PF: supervisor read access in kernel mode

#PF: error_code(0x0000) - not-present page

PGD 0 P4D 0

Oops: 0000 [#1] SMP

CPU: 4 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc2+ #75

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015

RIP: 0010:set_hv_tscchange_cb+0x15/0xa0

Code: <8b> 04 82 8b 15 12 17 85 01 48 c1 e0 20 48 0d ee 00 01 00 f6 c6 08

...

Call Trace:

kvm_arch_init+0x17c/0x280

kvm_init+0x31/0x330

vmx_init+0xba/0x13a

do_one_initcall+0x41/0x1c0

kern

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References