GHSA-69XH-7R26-Q3MW
Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 12:30In the Linux kernel, the following vulnerability has been resolved:
KVM: s390: Free guest debug data on vcpu destroy
kvm_s390_clear_bp_data() is only called from kvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or disables debugging. A vCPU that is destroyed while hardware breakpoints are still armed - the normal case when the VMM just exits or crashes - leaks hw_bp_info, hw_wp_info and all old_data buffers, since generic KVM frees the vCPU right after kvm_arch_vcpu_destroy().
That is bounded by MAX_BP_COUNT entries, so roughly 8 KiB per vCPU, but it is unbounded over VM lifetimes. The allocations are GFP_KERNEL_ACCOUNT, so the charge also outlives the exiting process and pins dying memcgs.
Fix by clearing the debug data on vCPU destruction. Calling it unconditionally is fine: struct kvm_vcpu is zero allocated, so for a vCPU that never enabled debugging the counters are 0 and the pointers NULL.
{
"affected": [],
"aliases": [
"CVE-2026-89923"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-16T11:17:01Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: s390: Free guest debug data on vcpu destroy\n\nkvm_s390_clear_bp_data() is only called from\nkvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or\ndisables debugging. A vCPU that is destroyed while hardware breakpoints\nare still armed - the normal case when the VMM just exits or crashes -\nleaks hw_bp_info, hw_wp_info and all old_data buffers, since generic KVM\nfrees the vCPU right after kvm_arch_vcpu_destroy().\n\nThat is bounded by MAX_BP_COUNT entries, so roughly 8 KiB per vCPU, but\nit is unbounded over VM lifetimes. The allocations are\nGFP_KERNEL_ACCOUNT, so the charge also outlives the exiting process and\npins dying memcgs.\n\nFix by clearing the debug data on vCPU destruction. Calling it\nunconditionally is fine: struct kvm_vcpu is zero allocated, so for a vCPU\nthat never enabled debugging the counters are 0 and the pointers NULL.",
"id": "GHSA-69xh-7r26-q3mw",
"modified": "2026-09-16T12:30:41Z",
"published": "2026-09-16T12:30:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89923"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/053f2068cf9b0654b651fed5ad7649d3deb982bf"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/544a5a665019cef394ce8bda97fa7a2cab253781"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6c996b12bbe4a6023076e8eee3cfaf2cc99db76c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9a32c4c6a6c23b7f5bf765eb5b83ba7f64a8ec63"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b5acacfdb8966abff91836c1c5bd7da59d8a526e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d6280fc540d8f4653c9b54a78cb747e128070f5e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e4d8b7f176b976474e0800ba71ee2dfa3ce263c9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e7f698b09d4a7c36b299acf680fc50fe868e2bcd"
}
],
"schema_version": "1.4.0",
"severity": []
}
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