CVE-2026-89513: RISC-V: KVM: Fix PMU event info array size overflow

CVE-2026-89513: RISC-V: KVM: Fix PMU event info array size overflow

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

RISC-V: KVM: Fix PMU event info array size overflow

SBI PMU EVENT_GET_INFO stores guest-controlled num_events * sizeof(*einfo)
in a 32-bit integer. On RV64, num_events = 0x10000001 makes 0x100000010
truncate to 16. KVM then allocates one entry but loops over the original
num_events, causing out-of-bounds reads and writes. A nested guest
triggered:

BUG: KASAN: slab-out-of-bounds in kvm_riscv_vcpu_pmu_event_info+0xa4/0x142
Read of size 4 at addr ff600000074d46b0 by task init/1
Call Trace:
[<ffffffff8006471c>] kvm_riscv_vcpu_pmu_event_info+0xa4/0x142
[<ffffffff800690c0>] kvm_sbi_ext_pmu_handler+0xca/0x268
[<ffffffff8006779e>] kvm_riscv_vcpu_sbi_ecall+0xec/0x1e6
[<ffffffff8006008c>] kvm_riscv_vcpu_exit+0x48c/0x540
[<ffffffff8005ea0a>] kvm_arch_vcpu_ioctl_run+0x37e/0xc80
Allocated by task 1:
 __kmalloc_noprof+0x19e/0x4b0
 kvm_riscv_vcpu_pmu_event_info+0x72/0x142
 kvm_sbi_ext_pmu_handler+0xca/0x268
 kvm_riscv_vcpu_sbi_ecall+0xec/0x1e6
 kvm_riscv_vcpu_exit+0x48c/0x540
 kvm_arch_vcpu_ioctl_run+0x37e/0xc80
The buggy address is located 0 bytes to the right of
 allocated 16-byte region [ff600000074d46a0, ff600000074d46b0)

Store the shared-memory size in size_t and reject multiplication overflow.
Allocate the guest-driven array with GFP_KERNEL_ACCOUNT so it is charged
to kmemcg, and use __GFP_NOWARN to suppress allocation failure warnings.
Use kvcalloc() to allow vmalloc fallback and an unsigned long loop index
to match num_events.

The Linux kernel CVE team has assigned CVE-2026-89513 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.18 with commit e309fd113b9f6c34672a487be08fecb7e12e7e29 and fixed in 7.2.4 with commit 82088f88c96b99c27a974d09b02c2b133262fadf
	Issue introduced in 6.18 with commit e309fd113b9f6c34672a487be08fecb7e12e7e29 and fixed in 7.3-rc1 with commit 735bc20c24187ca419c9d5e63860a54b91be34bd

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-89513
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	arch/riscv/kvm/vcpu_pmu.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/82088f88c96b99c27a974d09b02c2b133262fadf
	https://git.kernel.org/stable/c/735bc20c24187ca419c9d5e63860a54b91be34bd