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Fri, 25 Sep 2026 09:12:05 -0700 (PDT) From: Andrea Parri To: Jason Gunthorpe , Kevin Tian Cc: Andrea Parri , Joerg Roedel , Will Deacon , Robin Murphy , Shuah Khan , Joao Martins , Alex Williamson , Yishai Hadas , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 3/4] iommufd: Reject a zero-length dirty bitmap request Date: Fri, 25 Sep 2026 18:11:39 +0200 Message-ID: <20260925161142.189813-4-parri.andrea@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260925161142.189813-1-parri.andrea@gmail.com> References: <20260925161142.189813-1-parri.andrea@gmail.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit iommufd_check_iova_range() subtracts one from bitmap->length before it checks the length, so a zero-length request wraps to SIZE_MAX. With iova = 0 the wrapped value passes the overflow and alignment checks, and the request reaches iova_bitmap_alloc() with length 0. iova_bitmap_alloc() then sizes the bitmap from a length - 1 of SIZE_MAX, so mapped_total_index is effectively unbounded. The scan uses last_iova = ULONG_MAX, which spans the whole IOAS when an area is mapped at IOVA 0. Reject a zero length before the subtraction. Fixes: b9a60d6f850e ("iommufd: Add IOMMU_HWPT_GET_DIRTY_BITMAP") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Andrea Parri --- drivers/iommu/iommufd/io_pagetable.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c index 4e447ce74cf6c..283ab372e8da8 100644 --- a/drivers/iommu/iommufd/io_pagetable.c +++ b/drivers/iommu/iommufd/io_pagetable.c @@ -605,6 +605,9 @@ int iommufd_check_iova_range(struct io_pagetable *iopt, size_t iommu_pgsize = iopt->iova_alignment; u64 last_iova; + if (!bitmap->length) + return -EINVAL; + if (check_add_overflow(bitmap->iova, bitmap->length - 1, &last_iova)) return -EOVERFLOW; -- 2.53.0