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: 12065389 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=unavailable 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 B730DC433DB for ; Wed, 3 Feb 2021 21:20:06 +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 40BC364F72 for ; Wed, 3 Feb 2021 21:20:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 40BC364F72 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 988006EBFB; Wed, 3 Feb 2021 21:20:01 +0000 (UTC) Received: from mail-wm1-x32d.google.com (mail-wm1-x32d.google.com [IPv6:2a00:1450:4864:20::32d]) by gabe.freedesktop.org (Postfix) with ESMTPS id CB8236EB72 for ; Wed, 3 Feb 2021 21:19:59 +0000 (UTC) Received: by mail-wm1-x32d.google.com with SMTP id u14so1048638wmq.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=ogo2gz5BeH9FtE16XDOGVmpAwOdQ5Yhca5k9R1QMUgT/FnP7Jv+jee/BB1/Wzr5iJ+ eW5MhRPALPUHyoYsJ2+LY/LW0avrSP8VTP4cu57CIbElWEYJcH3bWoV1GVmxxLexvrjH 4ZLbCP7lH0pyIYbk4fCP6dvBWBonblg/gMAytk9nSAeJ5aYqdFi7UWB2AaCI08ipv5Mp QT0KUhQ7eybXQRs2/nHROwhsNkRoo72hwp7JWtY2OgmY1eW3gxQdcTWHuhksBG77yPuM s5VOM6n2dAnf+3zPFwImY8frGPTZG+JE558GblnelNa0a6XCQnSUpNyjdShPclbQmaWr 0ntw== X-Gm-Message-State: AOAM533FkbPmvOWYxxR9CYzeXDMVLqguStkAXPVueCslsUJQNjZpfOXD TWhV9eFsmXPK6GuQDUHCJXe33g== 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 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 Subject: [Intel-gfx] [PATCH] RFC: dma-buf: Require VM_SPECIAL vma for mmap X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & 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 , John Stultz , Daniel Vetter , Suren Baghdasaryan , Sumit Semwal , linux-media@vger.kernel.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" 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);