From patchwork Mon Oct 26 10:58:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11856451 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6FAB0921 for ; Mon, 26 Oct 2020 10:58:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 45B5D2225C for ; Mon, 26 Oct 2020 10:58:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="Dj3JiGZj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1772798AbgJZK6j (ORCPT ); Mon, 26 Oct 2020 06:58:39 -0400 Received: from mail-wr1-f66.google.com ([209.85.221.66]:42565 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1772759AbgJZK6i (ORCPT ); Mon, 26 Oct 2020 06:58:38 -0400 Received: by mail-wr1-f66.google.com with SMTP id j7so11841475wrt.9 for ; Mon, 26 Oct 2020 03:58:36 -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=hPo/Bw6tNC6m8oopvfckb4iPuUPePa6aSZ/PC8jTJPc=; b=Dj3JiGZjov+rk5affXGvGP9402wtp2GUCI8icP85Tk14pyc7sO08mAvUqY9YP9TGeP A3lLoHuo5jVARaEvOzFub0c3j9eUvziHGf75XEJy+mxqS9G+F35hsNps/M+jOSCEbRrn iMP7/8q7yuqHTOslFET3CcuoYiLv8HRbrH3ec= 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=hPo/Bw6tNC6m8oopvfckb4iPuUPePa6aSZ/PC8jTJPc=; b=SWUYt0vxAUSNQf3QpD3thLslpW53dGPzpJL+lVw4tC2ZBx4CSGRU81hcbx4RHL7Jh6 oKvoI2oba0pttzT0G7pr5kGFy1XtfkJ9VdiNBpFyVmi/ld/UqrTSbFELP+kgTtdWFbOq j4JP4asFfYGwM4pgZTcVO9S+VbbPEYc3nkQnWZ82GbRwWfHGp3WkcvkXtsSpu0/TPEnG KStcWbluH28rd2Zamq+pNbTEeEZZkXDqhQthCLU8X7jhqHZrW9Zbv2hnMihUIsDNDi/q gN6PVnOe2NvBpFDVkO02uAkbwM76m8A5NGY47Pcgh5oSdNbG2Io2vy3WPAv/haDwweNw pQjA== X-Gm-Message-State: AOAM532Hzidp9n32pICN+TAf3MscM+Q15UkEW+HsyW+ivePIUKCdy2vr KgYciq+S/tY8DKVL0/i9XVds6A== X-Google-Smtp-Source: ABdhPJzNhlXxW3KYH0jGVof/+LSlV2+9EbEWYrtjvdi1lIJzYS2SPhGh/0KYLFV4Ur5EShPJwSKVLw== X-Received: by 2002:adf:a354:: with SMTP id d20mr18311675wrb.29.1603709915546; Mon, 26 Oct 2020 03:58:35 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id w83sm21165156wmg.48.2020.10.26.03.58.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Oct 2020 03:58:34 -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 , Daniel Vetter , Jason Gunthorpe , Dan Williams , Kees Cook , Benjamin Herrensmidt , Dave Airlie , Andrew Morton , John Hubbard , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Chris Wilson Subject: [PATCH v4 07/15] mm: Close race in generic_access_phys Date: Mon, 26 Oct 2020 11:58:10 +0100 Message-Id: <20201026105818.2585306-8-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201026105818.2585306-1-daniel.vetter@ffwll.ch> References: <20201026105818.2585306-1-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") Signed-off-by: Daniel Vetter Cc: Jason Gunthorpe Cc: Dan Williams Cc: Kees Cook Cc: Benjamin Herrensmidt Cc: Dave Airlie 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 Cc: Chris Wilson Signed-off-by: Daniel Vetter --- v2: Fix inversion in the retry check (John). v4: While at it, use offset_in_page (Chris Wilson) --- include/linux/mm.h | 3 ++- mm/memory.c | 46 +++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 45 insertions(+), 4 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 eeae590e526a..1b46eae3b703 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4840,28 +4840,68 @@ 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; - int offset = addr & (PAGE_SIZE-1); + pte_t *ptep, pte; + spinlock_t *ptl; + int offset = offset_in_page(addr); + 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