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Thu, 28 Aug 2025 19:44:51 +0000 (GMT) Message-ID: <2b7f73a9-4683-421e-b8f6-5835711cecf3@linux.ibm.com> Date: Thu, 28 Aug 2025 12:44:50 -0700 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] iommu/s390: Fix memory corruption when using identity domain To: Matthew Rosato , joro@8bytes.org, schnelle@linux.ibm.com Cc: will@kernel.org, robin.murphy@arm.com, gerald.schaefer@linux.ibm.com, jgg@ziepe.ca, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, stable@vger.kernel.org, Cam Miller References: <20250827210828.274527-1-mjrosato@linux.ibm.com> Content-Language: en-US From: Farhan Ali In-Reply-To: <20250827210828.274527-1-mjrosato@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: AV-mHGV0hVcYWCe_DvOlapjxFbJMfbrb X-Authority-Analysis: v=2.4 cv=fbCty1QF c=1 sm=1 tr=0 ts=68b0b1b7 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=aNs30nL-xdb_lp8ugGoA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: AV-mHGV0hVcYWCe_DvOlapjxFbJMfbrb X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODI2MDA1NSBTYWx0ZWRfX6nFxbwFK3FxK dNiEe+iAmeg3ZlaLSVqrBsBwCDox4psf+AV4ySLCXxWJ0c4L5FbX8ukr1W4mOO2w2ApahCpBR0t +JZjzrWBEr4ArlPzuKnTKXNiurX0vYHIZT9EJ+fHPRNy+QjDc0pD+T1q7/1NAxNYCcpYRoS7tik HpRmf3S98LR5mQ48+GwBF3/4jx7sWR2fQ0UKPeeW3gZmH9TcfR4WlFpcoUCWc86e2igetGZwACX /UTR+KWMvpt7N30io0EKhpQznzpfNJGbLEAgwE1agaA63sWdQwlCQjpkz+utQ6xpCnl5HEB9w01 oEO8LjJn/UlB7NgZLn/KBsoiM4Xph23tQlLM0LZb86nzcBrJ082tlc9X+3+ATkG9qyLDFzJ8uz7 GUqIhdWC X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-28_04,2025-08-28_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 malwarescore=0 bulkscore=0 clxscore=1011 priorityscore=1501 impostorscore=0 adultscore=0 phishscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508260055 On 8/27/2025 2:08 PM, Matthew Rosato wrote: > zpci_get_iommu_ctrs() returns counter information to be reported as part > of device statistics; these counters are stored as part of the s390_domain. > The problem, however, is that the identity domain is not backed by an > s390_domain and so the conversion via to_s390_domain() yields a bad address > that is zero'd initially and read on-demand later via a sysfs read. > These counters aren't necessary for the identity domain; just return NULL > in this case. > > This issue was discovered via KASAN with reports that look like: > BUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device > when using the identity domain for a device on s390. > > Cc: stable@vger.kernel.org > Fixes: 64af12c6ec3a ("iommu/s390: implement iommu passthrough via identity domain") > Reported-by: Cam Miller > Signed-off-by: Matthew Rosato > --- > drivers/iommu/s390-iommu.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c > index 9c80d61deb2c..d7370347c910 100644 > --- a/drivers/iommu/s390-iommu.c > +++ b/drivers/iommu/s390-iommu.c > @@ -1032,7 +1032,8 @@ struct zpci_iommu_ctrs *zpci_get_iommu_ctrs(struct zpci_dev *zdev) > > lockdep_assert_held(&zdev->dom_lock); > > - if (zdev->s390_domain->type == IOMMU_DOMAIN_BLOCKED) > + if (zdev->s390_domain->type == IOMMU_DOMAIN_BLOCKED || > + zdev->s390_domain->type == IOMMU_DOMAIN_IDENTITY) > return NULL; > > s390_domain = to_s390_domain(zdev->s390_domain); > Reviewed-by: Farhan Ali