From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by kanga.kvack.org (Postfix) with ESMTP id 8407E8E0001 for ; Tue, 18 Dec 2018 04:38:29 -0500 (EST) Received: by mail-wr1-f72.google.com with SMTP id v16so4546408wru.8 for ; Tue, 18 Dec 2018 01:38:29 -0800 (PST) Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk. [2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by mx.google.com with ESMTPS id l2si1190306wmc.16.2018.12.18.01.38.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 01:38:28 -0800 (PST) Date: Tue, 18 Dec 2018 09:37:54 +0000 From: Russell King - ARM Linux Subject: Re: [PATCH v4 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range Message-ID: <20181218093754.GI26090@n2100.armlinux.org.uk> References: <20181217202209.GA8859@jordon-HP-15-Notebook-PC> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181217202209.GA8859@jordon-HP-15-Notebook-PC> Sender: owner-linux-mm@kvack.org List-ID: To: Souptick Joarder Cc: akpm@linux-foundation.org, willy@infradead.org, mhocko@suse.com, robin.murphy@arm.com, iamjoonsoo.kim@lge.com, treding@nvidia.com, keescook@chromium.org, m.szyprowski@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org On Tue, Dec 18, 2018 at 01:52:09AM +0530, Souptick Joarder wrote: > Convert to use vm_insert_range() to map range of kernel > memory to user vma. > > Signed-off-by: Souptick Joarder > --- > arch/arm/mm/dma-mapping.c | 21 +++++++-------------- > 1 file changed, 7 insertions(+), 14 deletions(-) > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index 661fe48..7cbcde5 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -1582,31 +1582,24 @@ static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma > void *cpu_addr, dma_addr_t dma_addr, size_t size, > unsigned long attrs) > { > - unsigned long uaddr = vma->vm_start; > - unsigned long usize = vma->vm_end - vma->vm_start; > + unsigned long page_count = vma_pages(vma); > struct page **pages = __iommu_get_pages(cpu_addr, attrs); > unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT; > unsigned long off = vma->vm_pgoff; > + int err; > > if (!pages) > return -ENXIO; > > - if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off) > + if (off >= nr_pages) > return -ENXIO; Are you sure you can make this change? You are restricting the offset to be within 0..nr_pages which ensures that the initial struct page that is passed to vm_insert_range() is valid, but I think the removal of the following check is unsafe. Your new vm_insert_range() function only checks page_count <= vma_pages(vma), which it will be since it _is_ vma_pages(vma). With the removal of the second condition, there will be nothing checking that (eg) off may be nr_pages - 1, and page_count=50, meaning that vm_insert_range() will walk off the end of the page array. Please take another look at this. What about the other callsites of your new function - do they have the same issue? -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up