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Thu, 6 Aug 2026 19:20:37 +0000 (GMT) Received: from [9.61.80.66] (unknown [9.61.80.66]) by smtpav02.dal12v.mail.ibm.com (Postfix) with ESMTP; Thu, 6 Aug 2026 19:20:37 +0000 (GMT) Message-ID: Date: Thu, 6 Aug 2026 15:20:37 -0400 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm() To: sashiko-reviews@lists.linux.dev Cc: Vasily Gorbik , linux-s390@vger.kernel.org, Alexander Gordeev , kvm@vger.kernel.org, Heiko Carstens , Jason Herne , Matthew Rosato , Christian Borntraeger References: <20260806173435.105044-1-akrowiak@linux.ibm.com> <20260806175651.C01F01F000E9@smtp.kernel.org> Content-Language: en-US From: Anthony Krowiak In-Reply-To: <20260806175651.C01F01F000E9@smtp.kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: xlQpqdsSjNB9CED-jtmSPHgVuEXKTwE8 X-Authority-Analysis: v=2.4 cv=e5k2j6p/ c=1 sm=1 tr=0 ts=6a74de88 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=RVB5ZjYeXRyjgiCplOgA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: xlQpqdsSjNB9CED-jtmSPHgVuEXKTwE8 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA2MDE1MSBTYWx0ZWRfX6wayXWIcgJls 1ptK/Z5ii4bO3pVlTc80AYV0Hgq0gf7bSGjSlCQlPnGKr3NzIMhCsritaCgvxE7dxSPdw0eiLfg K3Taxxi1+L8YHpG5DOvBqKabDNZUfQ8GneDcZaI4Ha84i8h9/YfFBvDsLF+tPiBaxC7nigqjM5z AoYkU0PAnsxE4giU6NcgvOnNS/nZ6nDGyJW3sJZ2TOOOwDrntiKH9DPljU8CnJ27ejiALBIH7TG /12x3GLL8WswN30bpJOSV/XQEQtoT3kcz3cJ03YO3QwpgQr9gqetXYeTdzvjOjpR1gQANxBPnXg ZFqZStxQfZnZNUukO6Sa+jkDfrGPoDtC5ifV+XDbuywDj7XfKygweC+kWtnOYLYP2Sbj6FFDIo7 S5dpaySEtbq5eu2KB88pYAS4w3AabIVJCA9F55A0O/zqlYnNHMXMOttVLm8MpK+9/4G+7pBBOGd hsHjxSwad5/ZRAGndBg== X-Proofpoint-Spam-Info: AW1haW4tMjYwODA2MDE1MSBTYWx0ZWRfXwcynspDTsYJG /JA3EjK5iZ6gxh9eI/AR/pWd5TYlyFa9H7WvgawQi5MZvzdEkgCgFfPCDDk4S9xOGUWR/WHxbBz QtId9i5lhCrEUf8oF3+AgUa9THwNeKo= 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=2026-08-06_02,2026-08-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 priorityscore=1501 adultscore=0 phishscore=0 clxscore=1015 malwarescore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608060151 On 8/6/26 1:56 PM, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > > Pre-existing issues: > - [High] Unconditional dereference of `matrix_mdev->kvm` when handling host AP configuration changes. > -- > > --- Patch [1]: [PATCH v5] s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm() --- > commit ea70bf8efc92cb332a90ca640bf9deec142d0044 > Author: Anthony Krowiak > s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm() > > This commit fixes a stale pointer use-after-free issue when another mdev is > already attached to a KVM instance. It avoids iterating the mdev_list under > the mdevs_lock by changing the rwsem lock order and checking if > kvm->arch.crypto.pqap_hook is already set. > >> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c >> index 44b3a1dcc1b36..99a0efd999ef9 100644 >> --- a/drivers/s390/crypto/vfio_ap_ops.c >> +++ b/drivers/s390/crypto/vfio_ap_ops.c > [ ... ] >> @@ -1883,18 +1881,15 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev) >> struct kvm *kvm = matrix_mdev->kvm; >> >> if (kvm && kvm->arch.crypto.crycbd) { >> - down_write(&kvm->arch.crypto.pqap_hook_rwsem); >> - kvm->arch.crypto.pqap_hook = NULL; >> - up_write(&kvm->arch.crypto.pqap_hook_rwsem); >> - >> get_update_locks_for_kvm(kvm); >> + kvm->arch.crypto.pqap_hook = NULL; >> >> kvm_arch_crypto_clear_masks(kvm); >> vfio_ap_mdev_reset_queues(matrix_mdev); >> - kvm_put_kvm(kvm); >> matrix_mdev->kvm = NULL; > [Severity: High] > This is a pre-existing issue, but can unattached mdevs cause a crash during > host AP configuration changes? > > If an mdev is created but not attached to a guest (meaning matrix_mdev->kvm > is NULL), and a host AP config change occurs, vfio_ap_on_cfg_changed() > eventually triggers vfio_ap_mdev_cfg_remove(): > > drivers/s390/crypto/vfio_ap_ops.c:vfio_ap_mdev_cfg_remove() { > ... > list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) { > mutex_lock(&matrix_mdev->kvm->lock); > ... > } > > Will this unconditionally dereference matrix_mdev->kvm and cause a panic > since it isn't checked for NULL? A similar path exists in > vfio_ap_mdev_hot_plug_cfg() as well. This was responded to for the same review comment in v4 of this patch. A separate patch is forthcoming with a fix for this. > >> >> release_update_locks_for_kvm(kvm); >> + kvm_put_kvm(kvm); >> } >> }