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Fri, 6 Feb 2026 14:35:56 +0000 (GMT) From: Claudio Imbrenda To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, nsg@linux.ibm.com, nrb@linux.ibm.com, seiden@linux.ibm.com, gra@linux.ibm.com, schlameuss@linux.ibm.com, hca@linux.ibm.com, svens@linux.ibm.com, agordeev@linux.ibm.com, gor@linux.ibm.com, david@kernel.org, gerald.schaefer@linux.ibm.com Subject: [PATCH v1 2/3] KVM: s390: vsie: Fix race in walk_guest_tables() Date: Fri, 6 Feb 2026 15:35:52 +0100 Message-ID: <20260206143553.14730-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260206143553.14730-1-imbrenda@linux.ibm.com> References: <20260206143553.14730-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=UdxciaSN c=1 sm=1 tr=0 ts=6985fc51 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=VnNF1IyMAAAA:8 a=Xpc-Ysi5efBL8YaAkn8A:9 X-Proofpoint-GUID: cvMZZ6C56l5uNO_0W_grA6bNS4zbJZ68 X-Proofpoint-ORIG-GUID: cvMZZ6C56l5uNO_0W_grA6bNS4zbJZ68 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjA2MDEwMyBTYWx0ZWRfX8eaA+g2L5y5e mhpJkcVgC2mPhZurKub/wuXPQlocACElyRN3uZabg37nEmr9s+fXvL1xZM1hI2H8scBpGzEyd6J 2BKJfSsgIUcggmBBKfwX27LFhjlP7ahV4RMpZitmxQugxgKztY7keRBSliIth3TZoZr2msU/PRu 2OWVRxC1Tl0QSSJukOtWgP4ilQ2qYB8rix0hJggl2RMEc5zVpJfD7jQi4YFsLZwUQtVHg9bkeBD FbkduN+d+psszlr6/QhMFSZquz979fwL+LMbJH9zzx7ivRTTnnJ/LhIDKT6KuPzocR6WdNnJmhI GMRDK67A8874bw1GB5r+4VQ0QEeyus5nq3Hu8k9/xBonwV4Xtvp/6gV/16xmqbocfULjm7fscA4 eAwMQDMfNXEQLaWcGfQjTGEayW1CeBghcoAWDyQDe2ndjyBDf6tlctWWMoYZOyGuNLtn5vk+5Z4 I1gGa9tdtX8luA7yuYA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-06_04,2026-02-05_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 impostorscore=0 lowpriorityscore=0 suspectscore=0 clxscore=1015 bulkscore=0 spamscore=0 phishscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2601150000 definitions=main-2602060103 Content-Type: text/plain; charset="utf-8" It is possible that walk_guest_tables() is called on a shadow gmap that has been removed already, in which case its parent will be NULL. In such case, return -EAGAIN and let the callers deal with it. Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") Signed-off-by: Claudio Imbrenda Acked-by: Janosch Frank --- arch/s390/kvm/gaccess.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index 67de47a81a87..4630b2a067ea 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -1287,7 +1287,10 @@ static int walk_guest_tables(struct gmap *sg, unsign= ed long saddr, struct pgtwal union asce asce; int rc; =20 + if (!parent) + return -EAGAIN; kvm =3D parent->kvm; + WARN_ON(!kvm); asce =3D sg->guest_asce; entries =3D get_entries(w); =20 --=20 2.52.0