From patchwork Fri Feb 5 13:41:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 12071201 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=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 D6A73C4332B for ; Fri, 5 Feb 2021 22:42:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C103564FF0 for ; Fri, 5 Feb 2021 22:42:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231260AbhBEWm1 (ORCPT ); Fri, 5 Feb 2021 17:42:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231293AbhBENmA (ORCPT ); Fri, 5 Feb 2021 08:42:00 -0500 Received: from mail-wm1-x331.google.com (mail-wm1-x331.google.com [IPv6:2a00:1450:4864:20::331]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0627DC061797 for ; Fri, 5 Feb 2021 05:41:20 -0800 (PST) Received: by mail-wm1-x331.google.com with SMTP id w4so6043093wmi.4 for ; Fri, 05 Feb 2021 05:41:19 -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:in-reply-to:references :mime-version:content-transfer-encoding; bh=GCaPcXl/zVoyH5ug7imo/Ptsoxk4zPxmqCZda8+3vCk=; b=Lg5I//U+jhljDep/tZbtlTBpL5Gqws3LZ1vaFmypVkTv0Zi1lCd9nNxhtmfF2IqrE1 AQoLvMyrj7A6O41YXJiLwrrXzI1tgbvquIvcCydeB8vwCbH1Zfs/jKFez7Su+Qmo+EKL oFVBD8wgDQ3lhywMaJ/EF47zwno3jVpfMEiOg= 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=GCaPcXl/zVoyH5ug7imo/Ptsoxk4zPxmqCZda8+3vCk=; b=Y35sJtLK3e8y6D39msZ7/U/jWs2bX9HJ/viJTa9qpbZsnR8u8T/Na3nU615ePH5ypr 0ceeYPkQ2jkK3reGJwBEQj0GQrURTTCd5V7Bh1VjDvXWF6RRHRkPlK5MlLx/3A26xigo WDRLRgFjQxPzyYSXo3guNu7y7+25W/reGHH6RmGwRwHXyIp7AFJZZrTQhFxh1j/mWiok y+iui+d5pgIRQvoruXy6ySbx9DiHyPrLPEb7opWafQikLZvu1SjqYGFE9/BTCozVtrcU PiTufq2cJBbGKSFZjgsRoWNzwKoXbpWDcIzSabTCO3Ga6FjC2PCnJsKJCBympM/wreiq rpQA== X-Gm-Message-State: AOAM533brBhxejMRKZwJqSoryeO02IEVehAThjq6dSmH0Yans4OdmAG4 ag4c87V+/xbZuLqPZ8sdDaMNMA== X-Google-Smtp-Source: ABdhPJxrEXwkznYjeTT/T1bKOmAFxHx1aF6QSVq23Pt2SeXnxTFe4vLc0aqZqhVVuO6mujFzLCYWAA== X-Received: by 2002:a1c:2783:: with SMTP id n125mr3673907wmn.74.1612532478791; Fri, 05 Feb 2021 05:41:18 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id b19sm8620382wmj.22.2021.02.05.05.41.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Feb 2021 05:41:18 -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_PFNMAP vma for mmap Date: Fri, 5 Feb 2021 14:41:13 +0100 Message-Id: <20210205134113.2834980-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210203211948.2529297-1-daniel.vetter@ffwll.ch> References: <20210203211948.2529297-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org 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_PFNMAP, 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. v2: Jason brought up that we also want to guarantee that all ptes have the pte_special flag set, to catch fast get_user_pages (on architectures that support this). Allowing VM_MIXEDMAP (like VM_SPECIAL does) would still allow vm_insert_page, but limiting to VM_PFNMAP will catch that. From auditing the various functions to insert pfn pte entires (vm_insert_pfn_prot, remap_pfn_range and all it's callers like dma_mmap_wc) it looks like VM_PFNMAP is already required anyway, so this should be the correct flag to check for. 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 --- 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..06cb1d2e9fdc 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_PFNMAP)); + + 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_PFNMAP)); + + return ret; } EXPORT_SYMBOL_GPL(dma_buf_mmap);