On Fri, Sep 13, 2013 at 10:23 AM, Thomas Hellstrom <thellstrom@xxxxxxxxxx> wrote: > As previously mentioned, copy_from_user should return -EFAULT, since the > VMAs are marked with VM_IO. It should not recurse into fault(), so evil > user-space looses. I haven't put a printk in the code to prove this, but gem mmap also sets VM_IO in drm_gem_mmap_obj. And we can very much hit our own fault handler and deadlock .... On a _very_ quick reading (and definitely not enough coffee yet for reading mm/* stuff) it looks like it's get_user_pages that will return an -EFAULT when hitting upon a VM_IO mapping (which makes sense since there's really no page backing it). Actually using get_user_pages was the original slowpath we've had in a few places until we've noticed that for pwrite that breaks legit userspace (the glBufferData(glMap)) use-case), so we've switched to lock dropping and proper slowpaths using copy_*_user everywhere instead of trying to pin the userspace storage with get_user_pages. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
