From mboxrd@z Thu Jan 1 00:00:00 1970 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=-15.8 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 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 7F91BC433DB for ; Mon, 18 Jan 2021 13:29:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3ABD922C9C for ; Mon, 18 Jan 2021 13:29:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404100AbhARN2s (ORCPT ); Mon, 18 Jan 2021 08:28:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392207AbhARN2l (ORCPT ); Mon, 18 Jan 2021 08:28:41 -0500 Received: from mail-wm1-x334.google.com (mail-wm1-x334.google.com [IPv6:2a00:1450:4864:20::334]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3FDAC061573 for ; Mon, 18 Jan 2021 05:28:00 -0800 (PST) Received: by mail-wm1-x334.google.com with SMTP id e15so7375341wme.0 for ; Mon, 18 Jan 2021 05:28:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=CIzsGliBbSopdadL1aItIFfvgfPFm1TH0AYXUH5P8f0=; b=EG1bU1Clp69oWVePE+R8+uBrdoblAVGgjD0Rsl1PG7Dtkt1Y5MiFJNJEr4ggev4ueL EqMjCrKKFrn3BdgZTy2G2l/JGR8hhIzxHrXcmcyRxs5NhCf0KUwPm42lZ7D10W+TbZyi yocTmgFxoWNwmtqj7G+KGa+17F+DHQp48HcJ8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=CIzsGliBbSopdadL1aItIFfvgfPFm1TH0AYXUH5P8f0=; b=h5CkMgrpg6w8cjARcejXmTT1GgKNsYeh2u4vkdCPRPVuYCF0qcQwYt1hP5fV+o4lkI ofVjr4FdM+5XCt9BL61Lk5uxPKevwdhE8oBqdQC0QcsMQNWMUAcb4W1QSxGKiCVeZCMt mmHj99NAKd5v4cs4SCmO58rjpyWVu/cXHcrRoKCfREYY7Of48diPWGijzzqkOO69sSaD DPP7poeu/jq2JXhxad9oVVqOy/NN/yasjrX9gttWkjzjz/0d2eK9NO/JlG7u++9RpVFB yKouozWoNf1q9toL09b48cRY8UHVAEyttFMDO+qPRXHs7sphtxYZNVOHRVh0qlyQ2NUW mfgw== X-Gm-Message-State: AOAM5333GJy4+g5U9SyNLmR9kTmywoYEB9RzYXe0lAoqHl9rSnGKc4tx k7anp9c6oghScm9sP6AU36Z2Ig== X-Google-Smtp-Source: ABdhPJynswhW/jHIjYf7YzQkhm6cv1Qf880du20KnNrjVLb6EYSgnJjXgAOQMSOVVdy6g+3DjqdirA== X-Received: by 2002:a7b:c5c7:: with SMTP id n7mr576249wmk.140.1610976479503; Mon, 18 Jan 2021 05:27:59 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id a130sm25804754wmf.4.2021.01.18.05.27.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Jan 2021 05:27:58 -0800 (PST) Date: Mon, 18 Jan 2021 14:27:56 +0100 From: Daniel Vetter To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Daniel Vetter , DRI Development , Intel Graphics Development , Chris Wilson , Daniel Vetter , Sumit Semwal , David Stevens , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org Subject: Re: [PATCH] dma-buf: Add debug option Message-ID: References: <20210115130219.3915789-1-daniel.vetter@ffwll.ch> <20210115164739.3958206-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Operating-System: Linux phenom 5.7.0-1-amd64 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Fri, Jan 15, 2021 at 07:52:53PM +0100, Christian König wrote: > Am 15.01.21 um 17:47 schrieb Daniel Vetter: > > We have too many people abusing the struct page they can get at but > > really shouldn't in importers. Aside from that the backing page might > > simply not exist (for dynamic p2p mappings) looking at it and using it > > e.g. for mmap can also wreak the page handling of the exporter > > completely. Importers really must go through the proper interface like > > dma_buf_mmap for everything. > > > > I'm semi-tempted to enforce this for dynamic importers since those > > really have no excuse at all to break the rules. > > > > Unfortuantely we can't store the right pointers somewhere safe to make > > sure we oops on something recognizable, so best is to just wrangle > > them a bit by flipping all the bits. At least on x86 kernel addresses > > have all their high bits sets and the struct page array is fairly low > > in the kernel mapping, so flipping all the bits gives us a very high > > pointer in userspace and hence excellent chances for an invalid > > dereference. > > > > v2: Add a note to the @map_dma_buf hook that exporters shouldn't do > > fancy caching tricks, which would blow up with this address scrambling > > trick here (Chris) > > > > Enable by default when CONFIG_DMA_API_DEBUG is enabled. > > > > v3: Only one copy of the mangle/unmangle code (Christian) > > > > v4: #ifdef, not #if (0day) > > > > v5: sg_table can also be an ERR_PTR (Chris, Christian) > > > > Reviewed-by: Chris Wilson (v2) > > Signed-off-by: Daniel Vetter > > Cc: Chris Wilson > > Cc: Sumit Semwal > > Cc: "Christian König" > > Cc: David Stevens > > Cc: linux-media@vger.kernel.org > > Cc: linaro-mm-sig@lists.linaro.org > > Reviewed-by: Christian König Stuffed into drm-misc-next, thanks for reviewing to both of you. -Daniel > > > --- > > drivers/dma-buf/Kconfig | 8 +++++++ > > drivers/dma-buf/dma-buf.c | 46 +++++++++++++++++++++++++++++++++++---- > > include/linux/dma-buf.h | 6 +++++ > > 3 files changed, 56 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig > > index 4f8224a6ac95..4e16c71c24b7 100644 > > --- a/drivers/dma-buf/Kconfig > > +++ b/drivers/dma-buf/Kconfig > > @@ -50,6 +50,14 @@ config DMABUF_MOVE_NOTIFY > > This is marked experimental because we don't yet have a consistent > > execution context and memory management between drivers. > > +config DMABUF_DEBUG > > + bool "DMA-BUF debug checks" > > + default y if DMA_API_DEBUG > > + help > > + This option enables additional checks for DMA-BUF importers and > > + exporters. Specifically it validates that importers do not peek at the > > + underlying struct page when they import a buffer. > > + > > config DMABUF_SELFTESTS > > tristate "Selftests for the dma-buf interfaces" > > default n > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > > index 1c9bd51db110..f264b70c383e 100644 > > --- a/drivers/dma-buf/dma-buf.c > > +++ b/drivers/dma-buf/dma-buf.c > > @@ -666,6 +666,34 @@ void dma_buf_put(struct dma_buf *dmabuf) > > } > > EXPORT_SYMBOL_GPL(dma_buf_put); > > +static void mangle_sg_table(struct sg_table *sg_table) > > +{ > > +#ifdef CONFIG_DMABUF_DEBUG > > + int i; > > + struct scatterlist *sg; > > + > > + /* To catch abuse of the underlying struct page by importers mix > > + * up the bits, but take care to preserve the low SG_ bits to > > + * not corrupt the sgt. The mixing is undone in __unmap_dma_buf > > + * before passing the sgt back to the exporter. */ > > + for_each_sgtable_sg(sg_table, sg, i) > > + sg->page_link ^= ~0xffUL; > > +#endif > > + > > +} > > +static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach, > > + enum dma_data_direction direction) > > +{ > > + struct sg_table *sg_table; > > + > > + sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); > > + > > + if (!IS_ERR_OR_NULL(sg_table)) > > + mangle_sg_table(sg_table); > > + > > + return sg_table; > > +} > > + > > /** > > * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list > > * @dmabuf: [in] buffer to attach device to. > > @@ -737,7 +765,7 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev, > > goto err_unlock; > > } > > - sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL); > > + sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL); > > if (!sgt) > > sgt = ERR_PTR(-ENOMEM); > > if (IS_ERR(sgt)) { > > @@ -784,6 +812,16 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, > > } > > EXPORT_SYMBOL_GPL(dma_buf_attach); > > +static void __unmap_dma_buf(struct dma_buf_attachment *attach, > > + struct sg_table *sg_table, > > + enum dma_data_direction direction) > > +{ > > + /* uses XOR, hence this unmangles */ > > + mangle_sg_table(sg_table); > > + > > + attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction); > > +} > > + > > /** > > * dma_buf_detach - Remove the given attachment from dmabuf's attachments list > > * @dmabuf: [in] buffer to detach from. > > @@ -802,7 +840,7 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) > > if (dma_buf_is_dynamic(attach->dmabuf)) > > dma_resv_lock(attach->dmabuf->resv, NULL); > > - dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir); > > + __unmap_dma_buf(attach, attach->sgt, attach->dir); > > if (dma_buf_is_dynamic(attach->dmabuf)) { > > dma_buf_unpin(attach); > > @@ -924,7 +962,7 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, > > } > > } > > - sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); > > + sg_table = __map_dma_buf(attach, direction); > > if (!sg_table) > > sg_table = ERR_PTR(-ENOMEM); > > @@ -987,7 +1025,7 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, > > if (dma_buf_is_dynamic(attach->dmabuf)) > > dma_resv_assert_held(attach->dmabuf->resv); > > - attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction); > > + __unmap_dma_buf(attach, sg_table, direction); > > if (dma_buf_is_dynamic(attach->dmabuf) && > > !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) > > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > > index 628681bf6c99..efdc56b9d95f 100644 > > --- a/include/linux/dma-buf.h > > +++ b/include/linux/dma-buf.h > > @@ -154,6 +154,12 @@ struct dma_buf_ops { > > * On failure, returns a negative error value wrapped into a pointer. > > * May also return -EINTR when a signal was received while being > > * blocked. > > + * > > + * Note that exporters should not try to cache the scatter list, or > > + * return the same one for multiple calls. Caching is done either by the > > + * DMA-BUF code (for non-dynamic importers) or the importer. Ownership > > + * of the scatter list is transferred to the caller, and returned by > > + * @unmap_dma_buf. > > */ > > struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *, > > enum dma_data_direction); > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch