From patchwork Fri Oct 23 12:21:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11852965 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 0206C17D4 for ; Fri, 23 Oct 2020 12:23:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9E3824650 for ; Fri, 23 Oct 2020 12:23:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="kxcHr9Xa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S463669AbgJWMXH (ORCPT ); Fri, 23 Oct 2020 08:23:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S463671AbgJWMXG (ORCPT ); Fri, 23 Oct 2020 08:23:06 -0400 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB2BDC0613D2 for ; Fri, 23 Oct 2020 05:23:05 -0700 (PDT) Received: by mail-wr1-x442.google.com with SMTP id x7so1596366wrl.3 for ; Fri, 23 Oct 2020 05:23:05 -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=kxcHr9XaGgdgUN/6f9tRbwBS2R7y8JekVykqE3uxv65hBKf0VpkNLgGxd8FIvRj750 nO7ickZUiLfE5Y0mI+ot8RAg1bvzM+pU+EnQr+/RtXjGmgjqqxLTca/kFkBVNTJKhQjr XwcE78fbKjpMmELfqkY2vXpXpf6p2WAexMqJ0= 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=dYGHAmFNCaWAKLfPx2Gm/MW/wLyShIR0Hrhs3/ghoPaAyTsHs4qlPqFNI+1432nImJ 31m+hu0anTcNqxV9VYZnaBkMFpdwTHOQ+myhIQzNjx7E5fA3QbyY3l1sc/MzwIOCOryV Ni0kA5Lv2CbATrX5G1WtLJdWhwr8oA79PGmn/Bw7hAbpa0aGsKEZoKe4TdROZ9az72Jf kUH2vfHRJwnBarPY6O5rswVKLuDixmYP3hSykTgHm4x9Pbpy/T1r/mBObcsLeazVmXxS GD9yUIFBoqeSRZ8yMyd6SPShccPgMa62APtE8dnU/UVg5ttgGRj1PraOwhQVR1Uww8z5 jxnQ== X-Gm-Message-State: AOAM5335wphFe1rYXC7uK+lhdLSBHVQO13MLYTtBUyU+0GrtgzLJuM2N Dw9QgJu4NaUe5KDwfT/PjfM/Lg== X-Google-Smtp-Source: ABdhPJwnPss/3+FXK73SGyn1ajFye9TH2uvE+XJgRwBdhY+CfV9NESKavPXc5txtoFVhV9XkRhrz0Q== X-Received: by 2002:adf:e8d0:: with SMTP id k16mr2306084wrn.362.1603455784579; Fri, 23 Oct 2020 05:23:04 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id y4sm3056484wrp.74.2020.10.23.05.23.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2020 05:23:03 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , Daniel Vetter , Daniel Vetter , Jason Gunthorpe , Dan Williams , Kees Cook , Benjamin Herrensmidt , Dave Airlie , Andrew Morton , John Hubbard , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, Chris Wilson Subject: [PATCH 36/65] mm: Close race in generic_access_phys Date: Fri, 23 Oct 2020 14:21:47 +0200 Message-Id: <20201023122216.2373294-36-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201023122216.2373294-1-daniel.vetter@ffwll.ch> References: <20201021163242.1458885-1-daniel.vetter@ffwll.ch> <20201023122216.2373294-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@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