From patchwork Wed Oct 7 16:44:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 268392 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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, 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 78ADAC47432 for ; Wed, 7 Oct 2020 16:45:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 20B2F215A4 for ; Wed, 7 Oct 2020 16:45:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="E4wIl1kh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728642AbgJGQpA (ORCPT ); Wed, 7 Oct 2020 12:45:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52724 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728267AbgJGQop (ORCPT ); Wed, 7 Oct 2020 12:44:45 -0400 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99086C0613DC for ; Wed, 7 Oct 2020 09:44:44 -0700 (PDT) Received: by mail-wr1-x441.google.com with SMTP id j2so2980667wrx.7 for ; Wed, 07 Oct 2020 09:44:44 -0700 (PDT) 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=y0cYv7pt2ajdPKJ71Sud+gUJyoyQWkHY61omgO6gUCQ=; b=E4wIl1khATPAWsmoahDSq5XJ9XB3/O17Fju2KtWFpZcnpDunS6aB2uzf/IAoSlz+9+ 5VxZXcG5teVG2C1MloXLK4xiaqUArGcDx8l8ZuU+9gaO8lbpEVnn6vpAnmLx4qTlAd8x TdyxsIClr7xEEKfXI/m8EFXclIzKOCjXa7FyM= 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=y0cYv7pt2ajdPKJ71Sud+gUJyoyQWkHY61omgO6gUCQ=; b=mQA0LQsa/KYq0CIoXAEWGN13g6Ov3Kkw6aF1S2rkJaYOYl55LPF9lYeoEYvI9hsEHr qPXn7OESPfrDAddDkUqIwQ3PL7wLqKS1cp/5qf7PHabg3aArPFNFy1TIkbJZHCRS1qpB Tib0NDfk0xbVJYWtMMRwhn5Fei/Bang/PflyZbj5KMzuSVRRRKNBPxrkh/ZDokkFmxmB A4O48P8Z0C1CE9yofnprDsgDvdpj27GtlbLTHHFT0vot0MEfmDvPIP90v59eSxXdZCF+ HPhUah3rEveQ6Wi2MFogvSbNYkbYytqwfJHbKA2oIDVtrWEWUatY8bvjxYdXiGE75G7n +mrQ== X-Gm-Message-State: AOAM532wEKd5j9CwA28AN5y5enzkKex2c5Kyd87IW2JQslvp8Gfzejpq alNhr3KGFgKznm6jAMDU8uVSQw== X-Google-Smtp-Source: ABdhPJyOhUNMEwwCQ+AEh8GM5Lra9AvYxZp9hFKsj4jVU6Oiy0Fq4b4Qf4lRUIggnlkhrBK3gQ/vuQ== X-Received: by 2002:a5d:51ca:: with SMTP id n10mr4539798wrv.222.1602089083290; Wed, 07 Oct 2020 09:44:43 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id z191sm3332280wme.40.2020.10.07.09.44.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Oct 2020 09:44:42 -0700 (PDT) From: Daniel Vetter To: DRI Development , LKML Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, linux-s390@vger.kernel.org, Daniel Vetter , Jason Gunthorpe , Dan Williams , Kees Cook , Rik van Riel , Benjamin Herrensmidt , Dave Airlie , Hugh Dickins , Andrew Morton , John Hubbard , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Daniel Vetter Subject: [PATCH 07/13] mm: close race in generic_access_phys Date: Wed, 7 Oct 2020 18:44:20 +0200 Message-Id: <20201007164426.1812530-8-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201007164426.1812530-1-daniel.vetter@ffwll.ch> References: <20201007164426.1812530-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org Way back it was a reasonable assumptions that iomem mappings never change the pfn range they point at. But this has changed: - gpu drivers dynamically manage their memory nowadays, invalidating ptes with unmap_mapping_range when buffers get moved - contiguous dma allocations have moved from dedicated carvetouts to cma regions. This means if we miss the unmap the pfn might contain pagecache or anon memory (well anything allocated with GFP_MOVEABLE) - even /dev/mem now invalidates mappings when the kernel requests that iomem region when CONFIG_IO_STRICT_DEVMEM is set, see 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims the region") Accessing pfns obtained from ptes without holding all the locks is therefore no longer a good idea. Fix this. Since ioremap might need to manipulate pagetables too we need to drop the pt lock and have a retry loop if we raced. While at it, also add kerneldoc and improve the comment for the vma_ops->access function. It's for accessing, not for moving the memory from iomem to system memory, as the old comment seemed to suggest. References: 28b2ee20c7cb ("access_process_vm device memory infrastructure") Cc: Jason Gunthorpe Cc: Dan Williams Cc: Kees Cook Cc: Rik van Riel Cc: Benjamin Herrensmidt Cc: Dave Airlie Cc: Hugh Dickins Cc: Andrew Morton Cc: John Hubbard Cc: Jérôme Glisse Cc: Jan Kara Cc: Dan Williams Cc: linux-mm@kvack.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-samsung-soc@vger.kernel.org Cc: linux-media@vger.kernel.org Signed-off-by: Daniel Vetter --- include/linux/mm.h | 3 ++- mm/memory.c | 44 ++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 44 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index acd60fbf1a5a..2a16631c1fda 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -566,7 +566,8 @@ struct vm_operations_struct { vm_fault_t (*pfn_mkwrite)(struct vm_fault *vmf); /* called by access_process_vm when get_user_pages() fails, typically - * for use by special VMAs that can switch between memory and hardware + * for use by special VMAs. See also generic_access_phys() for a generic + * implementation useful for any iomem mapping. */ int (*access)(struct vm_area_struct *vma, unsigned long addr, void *buf, int len, int write); diff --git a/mm/memory.c b/mm/memory.c index fcfc4ca36eba..8d467e23b44e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4873,28 +4873,68 @@ int follow_phys(struct vm_area_struct *vma, return ret; } +/** + * generic_access_phys - generic implementation for iomem mmap access + * @vma: the vma to access + * @addr: userspace addres, not relative offset within @vma + * @buf: buffer to read/write + * @len: length of transfer + * @write: set to FOLL_WRITE when writing, otherwise reading + * + * This is a generic implementation for &vm_operations_struct.access for an + * iomem mapping. This callback is used by access_process_vm() when the @vma is + * not page based. + */ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, void *buf, int len, int write) { resource_size_t phys_addr; unsigned long prot = 0; void __iomem *maddr; + pte_t *ptep, pte; + spinlock_t *ptl; int offset = addr & (PAGE_SIZE-1); + int ret = -EINVAL; + + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) + return -EINVAL; + +retry: + if (follow_pte(vma->vm_mm, addr, &ptep, &ptl)) + return -EINVAL; + pte = *ptep; + pte_unmap_unlock(ptep, ptl); - if (follow_phys(vma, addr, write, &prot, &phys_addr)) + prot = pgprot_val(pte_pgprot(pte)); + phys_addr = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT; + + if ((write & FOLL_WRITE) && !pte_write(pte)) return -EINVAL; maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot); if (!maddr) return -ENOMEM; + if (follow_pte(vma->vm_mm, addr, &ptep, &ptl)) + goto out_unmap; + + if (pte_same(pte, *ptep)) { + pte_unmap_unlock(ptep, ptl); + iounmap(maddr); + + goto retry; + } + if (write) memcpy_toio(maddr + offset, buf, len); else memcpy_fromio(buf, maddr + offset, len); + ret = len; + pte_unmap_unlock(ptep, ptl); +out_unmap: iounmap(maddr); - return len; + return ret; } EXPORT_SYMBOL_GPL(generic_access_phys); #endif