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Tue, 29 Sep 2026 02:49:07 -0700 (PDT) Received: from SurHub.localdomain ([196.188.113.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a00cf9b72fsm89821455e9.9.2026.09.29.02.49.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Sep 2026 02:49:07 -0700 (PDT) From: Abdifatah Suruur To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: alex@shazbot.org, eric.auger@redhat.com, smostafa@google.com, praan@google.com, ioana.ciornei@nxp.com, nipun.gupta@amd.com, nikhil.agarwal@amd.com Subject: [PATCH v2 7/7] vfio/cdx: reject non-shared MMIO mmaps Date: Tue, 29 Sep 2026 12:48:48 +0300 Message-ID: <20260929094848.7439-8-suruurism@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260929094848.7439-1-suruurism@gmail.com> References: <20260929094848.7439-1-suruurism@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vfio_cdx_mmap() accepts MAP_PRIVATE mappings. A non-shared mapping with VM_MAYWRITE is a COW mapping, and remap_pfn_range()'s COW special case in get_remap_pgoff() then overwrites vma->vm_pgoff with the physical frame number: if (is_cow) { if (addr != vm_start || end != vm_end) return -EINVAL; *vm_pgoff_p = pfn; } The VMA is inserted into the device file's mapping->i_mmap interval tree keyed by vm_pgoff, which VFIO expects to be the logical file offset: the core links every device mmap to the device inode's i_mapping precisely so that unmap_mapping_range() can revoke all mappings associated with a device (see vfio_device_cdev_open()). A raw PFN in vm_pgoff lands the interval tree entry in the wrong coordinate space, so unmap_mapping_range() cannot find the VMA and a stale MMIO mapping survives any revocation attempt. Without this check, a MAP_PRIVATE mapping reintroduces that corruption even with the logical-vm_pgoff fix in place. Require VM_SHARED as vfio-pci, vfio/fsl-mc and vfio/platform already do. This is defensive hygiene: vfio-cdx does not call unmap_mapping_range() today, so no reachable stale-mapping issue exists. Signed-off-by: Abdifatah Suruur --- drivers/vfio/cdx/main.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/vfio/cdx/main.c b/drivers/vfio/cdx/main.c index ea55b7767672c..28dc8c8256006 100644 --- a/drivers/vfio/cdx/main.c +++ b/drivers/vfio/cdx/main.c @@ -271,6 +271,9 @@ static int vfio_cdx_mmap(struct vfio_device *core_vdev, index = vma->vm_pgoff >> (VFIO_CDX_OFFSET_SHIFT - PAGE_SHIFT); + if (!(vma->vm_flags & VM_SHARED)) + return -EINVAL; + if (index >= cdx_dev->res_count) return -EINVAL; -- 2.53.0