# CVE-2024-47717: linux: In the Linux kernel, the following vulnerability has been resolved:  RISC-V: KVM: Don't zero-out PMU snapshot area be...

CVE-2024-47717 is fixed in linux on 1 platform, first by DEBIAN-CVE-2024-47717, released October 21, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2024-47717
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0022
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  RISC-V: KVM: Don't zero-out PMU snapshot area before freeing data  With the latest Linux-6.11-rc3, the below NULL pointer crash is observed when SBI PMU snapshot is enabled for the guest and the guest is forcefully powered-off.    Unable to handle kernel NULL pointer dereference at virtual address 0000000000000508   Oops [#1]   Modules linked in: kvm   CPU: 0 UID: 0 PID: 61 Comm: term-poll Not tainted 6.11.0-rc3-00018-g44d7178dd77a #3   Hardware name: riscv-virtio,qemu (DT)   epc : __kvm_write_guest_page+0x94/0xa6 [kvm]    ra : __kvm_write_guest_page+0x54/0xa6 [kvm]   epc : ffffffff01590e98 ra : ffffffff01590e58 sp : ffff8f80001f39b0    gp : ffffffff81512a60 tp : ffffaf80024872c0 t0 : ffffaf800247e000    t1 : 00000000000007e0 t2 : 0000000000000000 s0 : ffff8f80001f39f0    s1 : 00007fff89ac4000 a0 : ffffffff015dd7e8 a1 : 0000000000000086    a2 : 0000000000000000 a3 : ffffaf8000000000 a4 : ffffaf80024882c0    a5 : 0000000000000000 a6 : ffffaf800328d780 a7 : 00000000000001cc    s2 : ffffaf800197bd00 s3 : 00000000000828c4 s4 : ffffaf800248c000    s5 : ffffaf800247d000 s6 : 0000000000001000 s7 : 0000000000001000    s8 : 0000000000000000 s9 : 00007fff861fd500 s10: 0000000000000001    s11: 0000000000800000 t3 : 00000000000004d3 t4 : 00000000000004d3    t5 : ffffffff814126e0 t6 : ffffffff81412700   status: 0000000200000120 badaddr: 0000000000000508 cause: 000000000000000d   [<ffffffff01590e98>] __kvm_write_guest_page+0x94/0xa6 [kvm]   [<ffffffff015943a6>] kvm_vcpu_write_guest+0x56/0x90 [kvm]   [<ffffffff015a175c>] kvm_pmu_clear_snapshot_area+0x42/0x7e [kvm]   [<ffffffff015a1972>] kvm_riscv_vcpu_pmu_deinit.part.0+0xe0/0x14e [kvm]   [<ffffffff015a2ad0>] kvm_riscv_vcpu_pmu_deinit+0x1a/0x24 [kvm]   [<ffffffff0159b344>] kvm_arch_vcpu_destroy+0x28/0x4c [kvm]   [<ffffffff0158e420>] kvm_destroy_vcpus+0x5a/0xda [kvm]   [<ffffffff0159930c>] kvm_arch_destroy_vm+0x14/0x28 [kvm]   [<ffffffff01593260>] kvm_destroy_vm+0x168/0x2a0 [kvm]   [<ffffffff015933d4>] kvm_put_kvm+0x3c/0x58 [kvm]   [<ffffffff01593412>] kvm_vm_release+0x22/0x2e [kvm]  Clearly, the kvm_vcpu_write_guest() function is crashing because it is being called from kvm_pmu_clear_snapshot_area() upon guest tear down.  To address the above issue, simplify the kvm_pmu_clear_snapshot_area() to not zero-out PMU snapshot area from kvm_pmu_clear_snapshot_area() because the guest is anyway being tore down.  The kvm_pmu_clear_snapshot_area() is also called when guest changes PMU snapshot area of a VCPU but even in this case the previous PMU snaphsot area must not be zeroed-out because the guest might have reclaimed the pervious PMU snapshot area for some other purpose.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.11.2-1 | [DEBIAN-CVE-2024-47717](https://patchblox.com/security/data/fix/linux/debian-cve-2024-47717.md) | Oct 21, 2024 |
| Linux | linux Debian 14 | 6.11.2-1 | [DEBIAN-CVE-2024-47717](https://patchblox.com/security/data/fix/linux/debian-cve-2024-47717.md) | Oct 21, 2024 |

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