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Wed, 5 Aug 2026 11:05:11 +0000 (GMT) From: Christian Borntraeger To: KVM Cc: Christian Borntraeger , Janosch Frank , David Hildenbrand , linux-s390 , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Matthew Rosato , Douglas Freimuth Subject: [PATCH v3 7/8] KVM: s390: Free guest debug data on vcpu destroy Date: Wed, 5 Aug 2026 13:04:54 +0200 Message-ID: <20260805110455.7200-8-borntraeger@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260805110455.7200-1-borntraeger@linux.ibm.com> References: <20260805110455.7200-1-borntraeger@linux.ibm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: p0acmKKldYpokI-O1jsnmg-tstoNYng9 X-Proofpoint-ORIG-GUID: p0acmKKldYpokI-O1jsnmg-tstoNYng9 X-Proofpoint-Spam-Info: AW1haW4tMjYwODA1MDA4NiBTYWx0ZWRfX6Ddwpxso/B+L uQTIV48faHl69VHFtBNQrsCSjGBCZHK2SrjSpnlF3jh8EeO1v3w4+TmH8oonxUDPQfa0tpBYT8v KQW+m4IvIgWED98psUyAd1xIyvl9QWQ= X-Authority-Analysis: v=2.4 cv=K8cS2SWI c=1 sm=1 tr=0 ts=6a7318eb cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=FN5RJEE1uaSDo9arrcAA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA1MDA4NiBTYWx0ZWRfX17dDQR33HuVN 2STTiTpYpzA5UBmfMLbRW+3E95J0Otr7Y7bxH4bLWhPFh3qitZO7kqKwTcbGsmnofnK+mhSDuOB KscJ7AeEWnwR6x1bouNQRzoh5DlaYga7kqmzh7ToC8ZJiwad7LBb08mXaJFCaU036MtYDFfpMpr 9vFMoVIgutVdGRdefpFgyqwGtbFwkXAEatBUw8NeOuVEifr5SmU9FO2Qtyv4HX/zKJKlCFJh/VS yxZ8mjqDggFa/im1NRq93ynhrHHXC64z6Cgds8XFwB1Jq7IUSOhC5DRu+M7sa8OLPSLZ8VWPem7 LyYjTPFBe5rDDXmWE0maQK+sJNDlXWHw/fwbxG7zG+wn8TLg9LKYtjLKm3VuGBOks3UhZLMq7DW Yd5tzX6zbPFjWon48YMoGNo6CCa0uya5CeFKFtNdgWLiIY6kxhIHSrK6NQ+piI+el2q7a7ow368 /ZImwafOasTDXIO/r8Q== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-05_03,2026-08-04_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 impostorscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 phishscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608050086 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. Fixes: 27291e2165b6 ("KVM: s390: hardware support for guest debugging") Cc: stable@vger.kernel.org Signed-off-by: Christian Borntraeger Reviewed-by: Matthew Rosato --- arch/s390/kvm/kvm-s390.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index e0548926dc49..ccbdb109e22c 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -3409,6 +3409,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) trace_kvm_s390_destroy_vcpu(vcpu->vcpu_id); kvm_s390_clear_local_irqs(vcpu); kvm_clear_async_pf_completion_queue(vcpu); + kvm_s390_clear_bp_data(vcpu); if (!kvm_is_ucontrol(vcpu->kvm)) sca_del_vcpu(vcpu); kvm_s390_update_topology_change_report(vcpu->kvm, 1); -- 2.53.0