# CVE-2021-47390: linux: In the Linux kernel, the following vulnerability has been resolved:  KVM: x86: Fix stack-out-of-bounds memory access...

CVE-2021-47390 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47390, released May 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47390
- Priority: High
- CVSS: 7.1 (high)
- EPSS: 0.0026
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect()  KASAN reports the following issue:   BUG: KASAN: stack-out-of-bounds in kvm_make_vcpus_request_mask+0x174/0x440 [kvm]  Read of size 8 at addr ffffc9001364f638 by task qemu-kvm/4798   CPU: 0 PID: 4798 Comm: qemu-kvm Tainted: G               X --------- ---  Hardware name: AMD Corporation DAYTONA_X/DAYTONA_X, BIOS RYM0081C 07/13/2020  Call Trace:   dump_stack+0xa5/0xe6   print_address_description.constprop.0+0x18/0x130   ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm]   __kasan_report.cold+0x7f/0x114   ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm]   kasan_report+0x38/0x50   kasan_check_range+0xf5/0x1d0   kvm_make_vcpus_request_mask+0x174/0x440 [kvm]   kvm_make_scan_ioapic_request_mask+0x84/0xc0 [kvm]   ? kvm_arch_exit+0x110/0x110 [kvm]   ? sched_clock+0x5/0x10   ioapic_write_indirect+0x59f/0x9e0 [kvm]   ? static_obj+0xc0/0xc0   ? __lock_acquired+0x1d2/0x8c0   ? kvm_ioapic_eoi_inject_work+0x120/0x120 [kvm]  The problem appears to be that 'vcpu_bitmap' is allocated as a single long on stack and it should really be KVM_MAX_VCPUS long. We also seem to clear the lower 16 bits of it with bitmap_zero() for no particular reason (my guess would be that 'bitmap' and 'vcpu_bitmap' variables in kvm_bitmap_or_dest_vcpus() caused the confusion: while the later is indeed 16-bit long, the later should accommodate all possible vCPUs).

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.14.12-1 | [DEBIAN-CVE-2021-47390](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47390.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.14.12-1 | [DEBIAN-CVE-2021-47390](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47390.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.14.12-1 | [DEBIAN-CVE-2021-47390](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47390.md) | May 21, 2024 |

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