PT-2026-64362 · Linux · Linux
CVE-2026-64247
·
Publicado
2026-07-24
·
Atualizado
2026-07-24
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In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: hyper-v: Bound the bank index when querying sparse banks
When checking if a VP ID is included in a sparse bank set, explicitly check
that the ID can actually be contained in a sparse bank (the TLFS allows for
a maximum of 64 banks of 64 vCPUs each). When handling a paravirtual TLB
flush for L2, the VP ID is copied verbatim from the enlightened VMCS,
without any bounds check, i.e. isn't guaranteed to be under the limit of
4096.
Failure to check the bounds of the VP ID leads to an out-of-bounds read
when testing the sparse bank, and super strictly speaking could lead to KVM
performing an unnecessary TLB flush for an L2 vCPU.
==================================================================
BUG: KASAN: use-after-free in hv is vp in sparse set+0x85/0x100 [kvm]
Read of size 8 at addr ffff88811ba5f598 by task hyperv evmcs/2802
CPU: 12 UID: 1000 PID: 2802 Comm: hyperv evmcs Not tainted 7.1.0-rc2 #7 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Call Trace:
dump stack lvl+0x51/0x60
print report+0xcb/0x5d0
kasan report+0xb4/0xe0
kasan check range+0x35/0x1b0
hv is vp in sparse set+0x85/0x100 [kvm]
kvm hv flush tlb+0xe9e/0x16c0 [kvm]
kvm hv hypercall+0xe6b/0x1e60 [kvm]
vmx handle exit+0x485/0x1b60 [kvm intel]
kvm arch vcpu ioctl run+0x22e3/0x5070 [kvm]
kvm vcpu ioctl+0x5d0/0x10c0 [kvm]
x64 sys ioctl+0x129/0x1a0
do syscall 64+0xb9/0xcf0
entry SYSCALL 64 after hwframe+0x4b/0x53
RIP: 0033:0x7f0e62d1a9bf
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffffffffffffffff pfn:0x11ba5f
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 0000000000000000 00000000ffffffff 0000000000000000
raw: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88811ba5f480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88811ba5f500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88811ba5f580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88811ba5f600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88811ba5f680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== Disabling lock debugging due to kernel taint
Opportunistically add a compile time assertion to ensure the maximum number
of sparse banks exactly matches the number of possible bits in the passed
in mask.
[sean: add KASAN splat, drop comment, add assert, massage changelog]
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