From patchwork Wed Feb 3 21:19:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 71293 Received: from vger.kernel.org ([23.128.96.18]) by www.linuxtv.org with esmtp (Exim 4.92) (envelope-from ) id 1l7Pa5-009l5L-P3; Wed, 03 Feb 2021 21:20:58 +0000 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231550AbhBCVUk (ORCPT + 1 other); Wed, 3 Feb 2021 16:20:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231467AbhBCVUk (ORCPT ); Wed, 3 Feb 2021 16:20:40 -0500 Received: from mail-wm1-x336.google.com (mail-wm1-x336.google.com [IPv6:2a00:1450:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C5506C0613D6 for ; Wed, 3 Feb 2021 13:19:59 -0800 (PST) Received: by mail-wm1-x336.google.com with SMTP id w4so1136189wmi.4 for ; Wed, 03 Feb 2021 13:19:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0KFkS15Rzk/OuayxNy0U6nwvFrwjvOdNgW3QDiU+4sc=; b=B7EMeYtWrV2AdNBT7y1PBSR9YxDl9aaGbp4q9BWq9AqSEZX9pd79s3t/xli9kTbRB6 Xo/S/aN4oPc7Fu9md3ZQkcmMZ2qEZi9lZ8KtRMICl828jKRyISGJ6gnYUBenEUVvWGHs j5AjwWMz62ODeMu25iCr6b7IgeKTDPmOXwGoQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0KFkS15Rzk/OuayxNy0U6nwvFrwjvOdNgW3QDiU+4sc=; b=V6K7xz1DpLnRiTCm36Q2hzS5I10PCz7qC7gKjGiNOkUySU7G1SX8XYjU5IJfdWR5l1 8bhkxMyr40F/+43Sg2STGcl04z7dB4C+o3pIxEVP5/1x/sl9LKi3EhoSOJfpWRjuK0kT PmN0xCNlu3KXtCwbblB+8vukfEQ6S0xIrEz4xH8hTFgMHltYU74CZSO+kYYrJfyrBqog xSYKg2do2gs2E06fXqyMHC2/Y5SE4v0zOqaNysO7zhyscXfeuw/DCINus7oap6aIcvNe NsoP/UeEO3EIhrN18a8UeXwmQy9s3QrzAVsIvxMPc8OjD1j8/m8WisasDMl0jszEiWcJ u1AA== X-Gm-Message-State: AOAM532+ETiO/FV6YX2lYmDeYLlPeT0jOwZq8NIklahnVzebO8s6QSSM ikxQcyPTXCkRGQV+RX+XUDU2Bw== X-Google-Smtp-Source: ABdhPJzmU+Or9jzYUxXpAPVaDeRxSWgaJEx85VA2rMsPqlZffUGrONNNs7GEJYIhtZkMGnZTZpPI4g== X-Received: by 2002:a7b:c854:: with SMTP id c20mr4449864wml.127.1612387198566; Wed, 03 Feb 2021 13:19:58 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id j185sm4217399wma.1.2021.02.03.13.19.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Feb 2021 13:19:57 -0800 (PST) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , Daniel Vetter , Jason Gunthorpe , Suren Baghdasaryan , Matthew Wilcox , John Stultz , Daniel Vetter , Sumit Semwal , =?utf-8?q?Christian_K=C3=B6nig?= , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org Subject: [PATCH] RFC: dma-buf: Require VM_SPECIAL vma for mmap Date: Wed, 3 Feb 2021 22:19:48 +0100 Message-Id: <20210203211948.2529297-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.30.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-LSpam-Score: -2.5 (--) X-LSpam-Report: No, score=-2.5 required=5.0 tests=BAYES_00=-1.9,DKIM_SIGNED=0.1,DKIM_VALID=-0.1,DKIM_VALID_AU=-0.1,HEADER_FROM_DIFFERENT_DOMAINS=0.5,MAILING_LIST_MULTI=-1 autolearn=ham autolearn_force=no tldr; DMA buffers aren't normal memory, expecting that you can use them like that (like calling get_user_pages works, or that they're accounting like any other normal memory) cannot be guaranteed. Since some userspace only runs on integrated devices, where all buffers are actually all resident system memory, there's a huge temptation to assume that a struct page is always present and useable like for any more pagecache backed mmap. This has the potential to result in a uapi nightmare. To stop this gap require that DMA buffer mmaps are VM_SPECIAL, which blocks get_user_pages and all the other struct page based infrastructure for everyone. In spirit this is the uapi counterpart to the kernel-internal CONFIG_DMABUF_DEBUG. Motivated by a recent patch which wanted to swich the system dma-buf heap to vm_insert_page instead of vm_insert_pfn. References: https://lore.kernel.org/lkml/CAKMK7uHi+mG0z0HUmNt13QCCvutuRVjpcR0NjRL12k-WbWzkRg@mail.gmail.com/ Cc: Jason Gunthorpe Cc: Suren Baghdasaryan Cc: Matthew Wilcox Cc: John Stultz Signed-off-by: Daniel Vetter Cc: Sumit Semwal Cc: "Christian König" Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Acked-by: Christian König --- drivers/dma-buf/dma-buf.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index f264b70c383e..d3081fc07056 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -127,6 +127,7 @@ static struct file_system_type dma_buf_fs_type = { static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) { struct dma_buf *dmabuf; + int ret; if (!is_dma_buf_file(file)) return -EINVAL; @@ -142,7 +143,11 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) dmabuf->size >> PAGE_SHIFT) return -EINVAL; - return dmabuf->ops->mmap(dmabuf, vma); + ret = dmabuf->ops->mmap(dmabuf, vma); + + WARN_ON(!(vma->vm_flags & VM_SPECIAL)); + + return ret; } static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) @@ -1244,6 +1249,8 @@ EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access); int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, unsigned long pgoff) { + int ret; + if (WARN_ON(!dmabuf || !vma)) return -EINVAL; @@ -1264,7 +1271,11 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, vma_set_file(vma, dmabuf->file); vma->vm_pgoff = pgoff; - return dmabuf->ops->mmap(dmabuf, vma); + ret = dmabuf->ops->mmap(dmabuf, vma); + + WARN_ON(!(vma->vm_flags & VM_SPECIAL)); + + return ret; } EXPORT_SYMBOL_GPL(dma_buf_mmap);