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Userspace can map such a region read-only and then upgrade the mapping to writable with mprotect(), writing to FPGA port control/status registers the host owns. A guest assigned an AFU can use this to reconfigure or reset the port and interfere with other tenants on the same FPGA. Clear VM_MAYWRITE for regions without the WRITE flag, as i915 does for its read-only objects and as fixed in drm/vc4 (CVE-2026-68445) and drm/panthor (CVE-2024-53071) and ptp: vmclock (commit a5edadbae57e2298a56cf7a4e774a027905a331f). Fixes: 1a1527cf5ddac ("fpga: dfl: add FPGA Accelerated Function Unit driver basic framework") Cc: stable@vger.kernel.org Signed-off-by: Abdifatah Suruur --- --- a/drivers/fpga/dfl-afu-main.c +++ b/drivers/fpga/dfl-afu-main.c @@ -836,7 +836,11 @@ if ((vma->vm_flags & VM_WRITE) && !(region.flags & DFL_PORT_REGION_WRITE)) return -EPERM; + /* Prevent read-only port mappings from being upgraded with mprotect() */ + if (!(region.flags & DFL_PORT_REGION_WRITE)) + vm_flags_clear(vma, VM_MAYWRITE); + /* Support debug access to the mapping */ vma->vm_ops = &afu_vma_ops; vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);