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[34.105.23.239]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ae4cd40e4dsm108183855ad.92.2026.03.04.14.30.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Mar 2026 14:30:59 -0800 (PST) Date: Wed, 4 Mar 2026 22:30:55 +0000 From: David Matlack To: Alex Mastro Cc: Alex Williamson , Shuah Khan , kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vfio: selftests: fix crash in vfio_dma_mapping_mmio_test Message-ID: References: <20260303-fix-mmio-test-v1-1-78b4a9e46a4e@fb.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260303-fix-mmio-test-v1-1-78b4a9e46a4e@fb.com> On 2026-03-03 11:46 AM, Alex Mastro wrote: > Remove the __iommu_unmap() call on a region that was never mapped. > When __iommu_map() fails (expected for MMIO vaddrs in non-VFIO > modes), the region is not added to the dma_regions list, leaving its > list_head zero-initialized. If the unmap ioctl returns success, > __iommu_unmap() calls list_del_init() on this zeroed node and crashes. > > This fixes the iommufd_compat_type1 and iommufd_compat_type1v2 > test variants. > > Fixes: 080723f4d4c3 ("vfio: selftests: Add vfio_dma_mapping_mmio_test") > Signed-off-by: Alex Mastro > --- > The bug was missed because the test was originally run against a kernel > without commit afb47765f923 ("iommufd: Make vfio_compat's unmap succeed > if the range is already empty"). Without that fix, the unmap ioctl > returned -ENOENT, taking the early return before list_del_init(). Thanks for the fix. Looking back I remember testing your new test out without seeing a failure. Turns out I had applied it on top of tag vfio-v6.19-rc1, which did not have commit afb47765f923. Reviewed-by: David Matlack