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Thu, 23 Jul 2026 20:14:08 +0000 (GMT) Received: from [9.61.177.4] (unknown [9.61.177.4]) by smtpav05.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 23 Jul 2026 20:14:08 +0000 (GMT) Message-ID: <0dae69e7-8161-46e7-bef2-edabefd93fea@linux.ibm.com> Date: Thu, 23 Jul 2026 16:14:08 -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 6/6] KVM: s390: pci: Validate AIBV and AISB before pinning guest pages To: Farhan Ali , sashiko-reviews@lists.linux.dev Cc: Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-s390@vger.kernel.org, kvm@vger.kernel.org, Christian Borntraeger References: <20260723183440.3271-1-alifm@linux.ibm.com> <20260723183440.3271-7-alifm@linux.ibm.com> <20260723184802.816BE1F000E9@smtp.kernel.org> Content-Language: en-US From: Matthew Rosato In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzIzMDE5NiBTYWx0ZWRfX/6er4hjRenYA lsOWceQqDL6ZWvc/RJ6pYnPy75JcJGnWs/1y/V1OhlFm2/Qtp/dw91JpcvIHYJTv1AJSi1vScVP fZT2Ftr8UsJKw+cxF0BSDz8pNS/oUJJ1VFjEd3rAG+xBxyNDhbfibsD7+Erx/g9r6RaOvryHDja DLx2evIgNEd7oQJeXeQVWYF3BE0JT2+yKNvYU9zqOj/ASnQzmOjAAnBZigiZ286y2+LQha5gF5J APDAeBjgpg0Wqzx3Q1es6Wo1uFzuh05SZtyJMyLgKMf2mQXpvgLGoFuNhYsc/H/iJM6NqbG4DQZ CBb9xHW02eaLBeVwCuTd4y1zEsBaDK9tA07DppBjT9UIWItdCZE9i5rE5gTE/u8cmVM+NDRUgbi 41O0v9IyOnDZWyvL9+VxogZ2tq4G2I4KVuGqcQsowuJP/luTd8xkah2/3V+IhRFuJJBWEEZXquf NIhWfQlMajvfKd4qo0g== X-Authority-Analysis: v=2.4 cv=F7ZnsKhN c=1 sm=1 tr=0 ts=6a627614 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=s2hAA0MTUvO56OCXh08A:9 a=QEXdDO2ut3YA:10 a=zZCYzV9kfG8A:10 X-Proofpoint-ORIG-GUID: 51X4vgbx5dHs6aMcJZj0Sj_fdjr6YsV4 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzIzMDE5NiBTYWx0ZWRfX0qKSzKOJSI2e 2dSDXBqJijhCst3U2waq/SPvXma3KP458x7J0WmjVCqSMRh8kGwN7aP8Ylh5TjZ4nz+WNVvu55W PVrMLEwMn3GsN9XWQqDTR0tQiYkVXp4= X-Proofpoint-GUID: 51X4vgbx5dHs6aMcJZj0Sj_fdjr6YsV4 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=2026-07-23_06,2026-07-22_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 phishscore=0 bulkscore=0 clxscore=1011 priorityscore=1501 impostorscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607230196 >> [Severity: Critical] >> Does this calculation underestimate the true byte footprint of the bit >> vector >> when aibvo is non-zero? >> >> If a guest provides msi_vecs = 64, aibvo = 63, and an aibv GPA with a >> page >> offset of 4081, the calculated size is 15 bytes instead of 16. The npages >> calculation yields DIV_ROUND_UP(4081 + 15, 4096) = 1, which incorrectly >> passes the npages > 1 boundary check. >> >> This would result in KVM pinning only one page, but the hardware could >> access >> the 16th byte, writing to the first byte of the next unpinned host >> physical >> page, which could lead to host memory corruption. > > I think Sashiko does have a valid point here (sigh...). The right fix > would be to correctly round up both msi_vecs and aibvo bits so: > > size = BITS_TO_LONGS(msi_vecs + fib->fmt0.aibvo) * sizeof(unsigned long); > > and remove size += (fib->fmt0.aibvo / 8); > Yeah, that sounds right to me.