# CVE-2021-47217: linux: In the Linux kernel, the following vulnerability has been resolved:  x86/hyperv: Fix NULL deref in set_hv_tscchange_c...

CVE-2021-47217 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47217, released April 10, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-47217
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 10, 2024

## 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

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.15.5-1 | [DEBIAN-CVE-2021-47217](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47217.md) | Apr 10, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.15.5-1 | [DEBIAN-CVE-2021-47217](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47217.md) | Apr 10, 2024 |
| Linux | linux Debian 14 | 5.15.5-1 | [DEBIAN-CVE-2021-47217](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47217.md) | Apr 10, 2024 |

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