CVE-2021-47217

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

MEDIUM

5.5

CVSS Score

Published: April 10, 2024 at 07:01 PM UTC

Updated: June 17, 2026 at 04:16 AM UTC

1 product affected across 1 vendorLinux Kernel

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Severity

MEDIUM5.5

Exploit prediction

EPSS 0.2%

SSVC

No known exploit

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 kernel_init_freeable+0x1f2/0x23b kernel_init+0x16/0x120 ret_from_fork+0x22/0x30

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Linux Kernel · Linux

95%

4.16 ≤ v < 4.19.2184.16 ≤ v < 5.10.824.16 ≤ v < 5.15.54.16 ≤ v < 5.164.16 ≤ v < 5.4.1624.20 ≤ v < 5.4.1625.11 ≤ v < 5.15.55.5 ≤ v < 5.10.825.16 rc193286261de1b46339aa27cd4c639b21778f6cade

Vendor states this is fixed in 8823ea27fff6084bbb4bc71d15378fae0220b1d8 (fixed)

Vendor states this is fixed in 9c177eee116cf888276d3748cb176e72562cfd5c (fixed)

Vendor states this is fixed in b0e44dfb4e4c699cca33ede431b8d127e6e8d661 (fixed)

Vendor states this is fixed in b20ec58f8a6f4fef32cc71480ddf824584e24743 (fixed)

Vendor states this is fixed in daf972118c517b91f74ff1731417feb4270625a4 (fixed)

Vendor states this is fixed in 4.16 (unaffected)

Vendor states this is fixed in 4.19.218 (unaffected)

Vendor states this is fixed in 5.10.82 (unaffected)

Vendor states this is fixed in 5.15.5 (unaffected)

Vendor states this is fixed in 5.16 (unaffected)

Vendor states this is fixed in 5.4.162 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references