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: 12065385 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61565C433E0 for ; Wed, 3 Feb 2021 21:20:02 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8B29264E4E for ; Wed, 3 Feb 2021 21:20:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8B29264E4E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id BFED16EB72; Wed, 3 Feb 2021 21:20:00 +0000 (UTC) Received: from mail-wm1-x336.google.com (mail-wm1-x336.google.com [IPv6:2a00:1450:4864:20::336]) by gabe.freedesktop.org (Postfix) with ESMTPS id D5A9A6EBFB for ; Wed, 3 Feb 2021 21:19:59 +0000 (UTC) Received: by mail-wm1-x336.google.com with SMTP id 190so1167398wmz.0 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=AgaoTokwirOhYL+5t/hR3grz8lEh5Q7iXN0wONpbGK1bQ62H1B8l9Unprafq3BdPOV gtRHHPDWZiuCYlctDLjvGZ+UjyEU+0jKs7GiyrzLZL7qflW3Ry1y1c7y08KbCTyGGO5v D/muKj+DY7fWCC0/xxQpmryL98mN8oqoaavNsVCUNL1LPdDxHQLXr5d0csWiZcA38y2p ACk8GyC364GcSMRPwkFHreordEdgs12ZsvEHN1cAiF+xYn1qvVJGSZojAI3bQhdTuB68 7+yK85SC275MHuV0jfQkwUGMLbA1M8zx8bb63ke16FntJhy5Cwh7xNdAQiObI0utrPNc sLTw== X-Gm-Message-State: AOAM533+xZgr3jfxaBTzrT1fJn5WCM6KpluoPRcJUKpc9KdhwcpSzWod z+yFbAn9cFXYCLk1FhYL2VqF0vBhCmtTMvBt 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 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 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , Intel Graphics Development , Matthew Wilcox , =?utf-8?q?Christian_K=C3=B6nig?= , linaro-mm-sig@lists.linaro.org, Jason Gunthorpe , Daniel Vetter , Suren Baghdasaryan , linux-media@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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 Reported-by: kernel test robot --- 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);