{"id":"DEBIAN-CVE-2024-40953","details":"In the Linux kernel, the following vulnerability has been resolved:  KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()  Use {READ,WRITE}_ONCE() to access kvm-\u003elast_boosted_vcpu to ensure the loads and stores are atomic.  In the extremely unlikely scenario the compiler tears the stores, it's theoretically possible for KVM to attempt to get a vCPU using an out-of-bounds index, e.g. if the write is split into multiple 8-bit stores, and is paired with a 32-bit load on a VM with 257 vCPUs:    CPU0                              CPU1   last_boosted_vcpu = 0xff;                                      (last_boosted_vcpu = 0x100)                                     last_boosted_vcpu[15:8] = 0x01;   i = (last_boosted_vcpu = 0x1ff)                                     last_boosted_vcpu[7:0] = 0x00;    vcpu = kvm-\u003evcpu_array[0x1ff];  As detected by KCSAN:    BUG: KCSAN: data-race in kvm_vcpu_on_spin [kvm] / kvm_vcpu_on_spin [kvm]    write to 0xffffc90025a92344 of 4 bytes by task 4340 on cpu 16:   kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4112) kvm   handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel   vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? \t\t arch/x86/kvm/vmx/vmx.c:6606) kvm_intel   vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm   kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm   kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm   __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890)   __x64_sys_ioctl (fs/ioctl.c:890)   x64_sys_call (arch/x86/entry/syscall_64.c:33)   do_syscall_64 (arch/x86/entry/common.c:?)   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)    read to 0xffffc90025a92344 of 4 bytes by task 4342 on cpu 4:   kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4069) kvm   handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel   vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? \t\t\tarch/x86/kvm/vmx/vmx.c:6606) kvm_intel   vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm   kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm   kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm   __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890)   __x64_sys_ioctl (fs/ioctl.c:890)   x64_sys_call (arch/x86/entry/syscall_64.c:33)   do_syscall_64 (arch/x86/entry/common.c:?)   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)    value changed: 0x00000012 -\u003e 0x00000000","modified":"2026-09-15T09:03:09.547454559Z","published":"2024-07-12T13:15:17.560Z","upstream":["CVE-2024-40953"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-40953"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.99-1"}]}],"versions":["6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-40953.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.9.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-40953.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.9.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-40953.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}