Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1433050AbdDYTib (ORCPT ); Tue, 25 Apr 2017 15:38:31 -0400 Received: from mail-qk0-f169.google.com ([209.85.220.169]:35205 "EHLO mail-qk0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934352AbdDYTiY (ORCPT ); Tue, 25 Apr 2017 15:38:24 -0400 Subject: Re: [PATCH] arm64: Do not leave an invalid area->pages pointer in dma_common_contiguous_remap() To: Catalin Marinas , linux-kernel@vger.kernel.org References: <1493144543-2497-1-git-send-email-catalin.marinas@arm.com> Cc: linux-arm-kernel@lists.infradead.org, geert@linux-m68k.org, a.hajda@samsung.com, robin.murphy@arm.com, Greg Kroah-Hartman From: Laura Abbott Message-ID: Date: Tue, 25 Apr 2017 12:38:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <1493144543-2497-1-git-send-email-catalin.marinas@arm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3412 Lines: 99 On 04/25/2017 11:22 AM, Catalin Marinas wrote: > The dma_common_pages_remap() function allocates a vm_struct object and > initialises the pages pointer to value passed as argument. However, when > this function is called dma_common_contiguous_remap(), the pages array > is only temporarily allocated, being freed shortly after > dma_common_contiguous_remap() returns. Architecture code checking the > validity of an area->pages pointer would incorrectly dereference already > freed pointers. This has been exposed by the arm64 commit 44176bb38fa4 > ("arm64: Add support for DMA_ATTR_FORCE_CONTIGUOUS to IOMMU"). > > Fixes: 513510ddba96 ("common: dma-mapping: introduce common remapping functions") > Cc: Laura Abbott > Cc: Greg Kroah-Hartman > Reported-by: Andrzej Hajda > Signed-off-by: Catalin Marinas Acked-by: Laura Abbott > --- > > This is for correctness since once the arm64's mmap and get_sgtable ops > are fixed for DMA_ATTR_FORCE_CONTIGUOUS, we would no longer see the > issue. Anyway, it's better to get this fixed in case others trip over a > similar issue. I added a "Fixes" tag for completeness but I'm not sure > it's worth back-porting. > > drivers/base/dma-mapping.c | 29 ++++++++++++++++++++++------- > 1 file changed, 22 insertions(+), 7 deletions(-) > > diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c > index efd71cf4fdea..ab7071041141 100644 > --- a/drivers/base/dma-mapping.c > +++ b/drivers/base/dma-mapping.c > @@ -277,8 +277,8 @@ EXPORT_SYMBOL(dma_common_mmap); > * remaps an array of PAGE_SIZE pages into another vm_area > * Cannot be used in non-sleeping contexts > */ > -void *dma_common_pages_remap(struct page **pages, size_t size, > - unsigned long vm_flags, pgprot_t prot, > +static struct vm_struct *__dma_common_pages_remap(struct page **pages, > + size_t size, unsigned long vm_flags, pgprot_t prot, > const void *caller) > { > struct vm_struct *area; > @@ -287,13 +287,26 @@ void *dma_common_pages_remap(struct page **pages, size_t size, > if (!area) > return NULL; > > - area->pages = pages; > - > if (map_vm_area(area, prot, pages)) { > vunmap(area->addr); > return NULL; > } > > + return area; > +} > + > +void *dma_common_pages_remap(struct page **pages, size_t size, > + unsigned long vm_flags, pgprot_t prot, > + const void *caller) > +{ > + struct vm_struct *area; > + > + area = __dma_common_pages_remap(pages, size, vm_flags, prot, caller); > + if (!area) > + return NULL; > + > + area->pages = pages; > + > return area->addr; > } > > @@ -308,7 +321,7 @@ void *dma_common_contiguous_remap(struct page *page, size_t size, > { > int i; > struct page **pages; > - void *ptr; > + struct vm_struct *area; > unsigned long pfn; > > pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL); > @@ -318,11 +331,13 @@ void *dma_common_contiguous_remap(struct page *page, size_t size, > for (i = 0, pfn = page_to_pfn(page); i < (size >> PAGE_SHIFT); i++) > pages[i] = pfn_to_page(pfn + i); > > - ptr = dma_common_pages_remap(pages, size, vm_flags, prot, caller); > + area = __dma_common_pages_remap(pages, size, vm_flags, prot, caller); > > kfree(pages); > > - return ptr; > + if (!area) > + return NULL; > + return area->addr; > } > > /* >