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Wed, 29 Jul 2026 12:28:29 +0000 (GMT) Received: from [9.224.77.173] (unknown [9.224.77.173]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 29 Jul 2026 12:28:29 +0000 (GMT) Message-ID: Date: Wed, 29 Jul 2026 14:28:28 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 01/13] KVM: s390: Fix unlikely NULL gmap dereference To: Claudio Imbrenda , linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com References: <20260728170708.294400-1-imbrenda@linux.ibm.com> <20260728170708.294400-2-imbrenda@linux.ibm.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <20260728170708.294400-2-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: sEULQp11A-S0uilTdm_gU99Z8_kcLH6s X-Proofpoint-ORIG-GUID: sEULQp11A-S0uilTdm_gU99Z8_kcLH6s X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI5MDEwMiBTYWx0ZWRfX4xzV3rC9JfF3 B77dhcXq0JPOyFudGnhTY44QUSq6YwE8thJ2VrgYpBaDfiTt+uAmFEpxpJjIL7objOtgjM0IsZc jaLGlDT1ek7ii2EYpT6cp3wNqf5swYB1Hbcbn5o5G0Rd8KuYO3WbRjLdkY4R3YNww//yjXlXjOi MPb+0QFEyRMfreNuTkh070RF8TzXyxUb1952K9FlJQVl3ngI+dmxSaNuT8OmuA9v1LCC/3CnlYq AFPHrHBHnVGwyC8NHvg70nlxDDqMDGfgm33nkrT78I0Wgl2M8u6QmmE9My4P8m7E3P9WnSIsax4 SgRD+RecVTQgBGy54hdIKB2gV8Lbmw+BO6KFby7yg7nuDggrIKr/7VQAS2BVmiVsiy7IMV/PA8Z cTUTiajjR9yjqd75jolL2hSXx6AeBxByCVkiPKHe7/TbnZGBNmWUH7lWfSNBtyEyl/sqJLUUZ1F qHapDpFULoL4+d82jUw== X-Authority-Analysis: v=2.4 cv=SKFykuvH c=1 sm=1 tr=0 ts=6a69f1f3 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=_BKb5qho9Nre88LnVS8A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI5MDEwMiBTYWx0ZWRfX3HRyr0e3RoYW 8zwOwFejkorPkAV7gzkw2kprjFNnzKQ1x0DJkFhmpk2r9GY+YR8Mm19Bi24wedvZK+UTmDjXQ+k aCwp6p4pZRFXZ5IGntZYsS3wZ1MzCg4= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-29_04,2026-07-28_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 phishscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607290102 Am 28.07.26 um 19:06 schrieb Claudio Imbrenda: > When creating a new vCPU, kvm_vm_ioctl_create_vcpu() will call > kvm_arch_vcpu_postcreate() after the file descriptor for the new vCPU > has been created. The new file descriptor has not been returned yet, > but a malicious userspace program could try to guess it. > > If a malicious userspace program manages to start the newly created vCPU > before kvm_arch_vcpu_postcreate() is called, __vcpu_run() will try to > dereference vcpu->arch.gmap and trigger a NULL pointer dereference. > > Fix this by adding a new field to struct kvm_vcpu_arch to keep track of > the initialization status of the vCPU. Refuse to run a vCPU that is not > fully initialized. > > Fixes: dafd032a15f8 ("KVM: s390: move vcpu specific initalization to a later point") > Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") > Signed-off-by: Claudio Imbrenda > Reviewed-by: Steffen Eiden > Reviewed-by: Janosch Frank Reviewed-by: Christian Borntraeger