From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f74.google.com (mail-wr1-f74.google.com [209.85.221.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4874C32E12F for ; Mon, 24 Nov 2025 20:08:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764014902; cv=none; b=dvPKSE5ASfJUHj7T8sa/ePzYo0UQS7JJrZ1/ReZPvjPpv7Cqb3BCmKJxg0/8770u6FbxfV7i1oEvfuwtaB2Ovxdk4SoGAfK12lMzaiaZ4VKsC3y1OKV4tqLMxve2xrjo0Kf+8oRM3JGgXC1jBb/0GTWvxs4F0ccjoDcAmRqbWxc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764014902; c=relaxed/simple; bh=sBjQYtmJhyegaxt3+pEDMoSONwYUdW7o3IoGIm0ovYs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=kWeV25duQuxzOXeCu4OpfsWIUZfJXO9V/QHtlerq2mueRhC+dhCHItii48vvP/F/di0gjevzZitC8yPkKPsxI3/HlAUMWQFj4+IaW9SLkcGuSu65FJalXKJO6TAjv+sYmMZPt/bQANIee7pVPoeTZ0r2R1RbsM8KRAyc+LcItbU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--smostafa.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=vz3/GQcS; arc=none smtp.client-ip=209.85.221.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--smostafa.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="vz3/GQcS" Received: by mail-wr1-f74.google.com with SMTP id ffacd0b85a97d-42b2ad29140so2752216f8f.0 for ; Mon, 24 Nov 2025 12:08:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1764014898; x=1764619698; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=hbVDtgb8rBp8ziR20f2VdPbPb3JDkOdyP9SxZ3vHtis=; b=vz3/GQcSMQ0jg2s5SF1Q95KnTWRprvhcj9Ssb1whwgS094XYiHChvqpCBhb1Mho/bG jNW7/yKQMl0XRgRLAMCiWKYL96ZmmPMANsP3/A5cvu6K0ud8OIs41YvaFtndWcsqzvxr XkpGMSbPWXKrx/9m93gCdbQ8I5E5wVLT9npRkfFweFSA14ytsTzervoymHeX238g43GQ 0yF4LwkSBA2NBvGoGKSr0319Dlql+KsbhzvoyaJQd6UevIV20RBBpZxivHrML/cDwaHt yV2ORGJAPe3G3i0t8iOKDogApUgM85x2aRBNqaOHXP8NZ4pratvqZVWhydOh9MBeKFcD dLAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764014898; x=1764619698; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=hbVDtgb8rBp8ziR20f2VdPbPb3JDkOdyP9SxZ3vHtis=; b=hvdACJPILFonT8H/11gpSx9aC/uAKa3LyjOGXa3MZyGGmxRoPQn9AWfGBpUGf7ltdn BSttBsCwMmpRoS+AvWl/aGZPg0RtEQrstj48DMVYWD2J6ce6vCJv+DF0ujnAtq+L/1/q EOB5+7fhuE+bwvFQiHPqLVfsA/xOhVY3StgHKwY7R+dTs+IHO+3To0fSDXd1d95hyFy3 modeSXQeb8xB3JrCNbY1FLHzA/8w2uO41o0koiPpvWzHJcMs2+h0wz3eb9p5drKGkHbN opNdPDnUMLIqLDjPEdmOAV7scQTO3vXJt9HTkE7LpKNsyPD8aDWcn2OAG0DmMMYYDw06 otYQ== X-Forwarded-Encrypted: i=1; AJvYcCV3w/91gvxwCzpcqVL8yXisHVQri3bYsrWbaG30c7ydkkTAHqKIGh78gi0UOxIq2Uq32bHRHw==@lists.linux.dev X-Gm-Message-State: AOJu0YxDJ81h89ZFKScwHUGIkdEYBQHGKUnDdzxroLmr2CV4YUo9awVX n2qoixMnADQy5UswSo9keuFZLK62y9CGIU1LX+vSwtY7yGk6QazTgxb7Dyl7jE7kM3ac0wLING7 SqAA+DKSE9ASgwg== X-Google-Smtp-Source: AGHT+IELGZPf6DUHRoEs9He1ETOOPZ7Kr5+C1bY4CAkNyhB8outgBkxo6CndGZpyoRi8wlt+uNVgOnWJUV6+6A== X-Received: from wrbev10.prod.google.com ([2002:a05:6000:23ca:b0:429:8b8f:9db4]) (user=smostafa job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:2384:b0:42b:3b55:8927 with SMTP id ffacd0b85a97d-42cc1cba760mr13711892f8f.21.1764014898472; Mon, 24 Nov 2025 12:08:18 -0800 (PST) Date: Mon, 24 Nov 2025 20:08:08 +0000 In-Reply-To: <20251124200811.2942432-1-smostafa@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251124200811.2942432-1-smostafa@google.com> X-Mailer: git-send-email 2.52.0.460.gd25c4c69ec-goog Message-ID: <20251124200811.2942432-2-smostafa@google.com> Subject: [PATCH v3 1/4] drivers/iommu: Add page_ext for IOMMU_DEBUG_PAGEALLOC From: Mostafa Saleh To: linux-mm@kvack.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Cc: corbet@lwn.net, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, xiaqinxin@huawei.com, Mostafa Saleh Content-Type: text/plain; charset="UTF-8" Add a new config IOMMU_DEBUG_PAGEALLOC, which registers new data to page_ext. This config will be used by the IOMMU API to track pages mapped in the IOMMU to catch drivers trying to free kernel memory that they still map in their domains, causing all types of memory corruption. This behaviour is disabled by default and can be enabled using kernel cmdline iommu.debug_pagealloc. Signed-off-by: Mostafa Saleh --- .../admin-guide/kernel-parameters.txt | 6 ++++ drivers/iommu/Kconfig | 19 +++++++++++ drivers/iommu/Makefile | 1 + drivers/iommu/iommu-debug-pagealloc.c | 32 +++++++++++++++++++ include/linux/iommu-debug-pagealloc.h | 17 ++++++++++ mm/page_ext.c | 4 +++ 6 files changed, 79 insertions(+) create mode 100644 drivers/iommu/iommu-debug-pagealloc.c create mode 100644 include/linux/iommu-debug-pagealloc.h diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6c42061ca20e..dddf435a1c11 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2557,6 +2557,12 @@ 1 - Bypass the IOMMU for DMA. unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. + iommu.debug_pagealloc= + [KNL,EARLY] When CONFIG_IOMMU_DEBUG_PAGEALLOC is set, this + parameter enables the feature at boot time. By default, it + is disabled and the system behave the same way as a kernel + built without CONFIG_IOMMU_DEBUG_PAGEALLOC. + io7= [HW] IO7 for Marvel-based Alpha systems See comment before marvel_specify_io7 in arch/alpha/kernel/core_marvel.c. diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index 70d29b14d851..c9c1a1c1820e 100644 --- a/drivers/iommu/Kconfig +++ b/drivers/iommu/Kconfig @@ -383,4 +383,23 @@ config SPRD_IOMMU Say Y here if you want to use the multimedia devices listed above. +config IOMMU_DEBUG_PAGEALLOC + bool "Debug IOMMU mappings against page allocations" + depends on DEBUG_PAGEALLOC && IOMMU_API && PAGE_EXTENSION + help + This enables a consistency check between the kernel page allocator and + the IOMMU subsystem. It verifies that pages being allocated or freed + are not currently mapped in any IOMMU domain. + + This helps detect DMA use-after-free bugs where a driver frees a page + but forgets to unmap it from the IOMMU, potentially allowing a device + to overwrite memory that the kernel has repurposed. + + These checks are best-effort and may not detect all problems. + + Due to performance overhead, this feature is disabled by default. + You must enable "iommu.debug_pagealloc" from the kernel command + line to activate the runtime checks. + + If unsure, say N. endif # IOMMU_SUPPORT diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile index 355294fa9033..8f5130b6a671 100644 --- a/drivers/iommu/Makefile +++ b/drivers/iommu/Makefile @@ -34,3 +34,4 @@ obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o obj-$(CONFIG_SPRD_IOMMU) += sprd-iommu.o obj-$(CONFIG_APPLE_DART) += apple-dart.o +obj-$(CONFIG_IOMMU_DEBUG_PAGEALLOC) += iommu-debug-pagealloc.o diff --git a/drivers/iommu/iommu-debug-pagealloc.c b/drivers/iommu/iommu-debug-pagealloc.c new file mode 100644 index 000000000000..4022e9af7f27 --- /dev/null +++ b/drivers/iommu/iommu-debug-pagealloc.c @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2025 - Google Inc + * Author: Mostafa Saleh + * IOMMU API debug page alloc sanitizer + */ +#include +#include +#include +#include + +static bool needed; + +struct iommu_debug_metadata { + atomic_t ref; +}; + +static __init bool need_iommu_debug(void) +{ + return needed; +} + +struct page_ext_operations page_iommu_debug_ops = { + .size = sizeof(struct iommu_debug_metadata), + .need = need_iommu_debug, +}; + +static int __init iommu_debug_pagealloc(char *str) +{ + return kstrtobool(str, &needed); +} +early_param("iommu.debug_pagealloc", iommu_debug_pagealloc); diff --git a/include/linux/iommu-debug-pagealloc.h b/include/linux/iommu-debug-pagealloc.h new file mode 100644 index 000000000000..83e64d70bf6c --- /dev/null +++ b/include/linux/iommu-debug-pagealloc.h @@ -0,0 +1,17 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2025 - Google Inc + * Author: Mostafa Saleh + * IOMMU API debug page alloc sanitizer + */ + +#ifndef __LINUX_IOMMU_DEBUG_PAGEALLOC_H +#define __LINUX_IOMMU_DEBUG_PAGEALLOC_H + +#ifdef CONFIG_IOMMU_DEBUG_PAGEALLOC + +extern struct page_ext_operations page_iommu_debug_ops; + +#endif /* CONFIG_IOMMU_DEBUG_PAGEALLOC */ + +#endif /* __LINUX_IOMMU_DEBUG_PAGEALLOC_H */ diff --git a/mm/page_ext.c b/mm/page_ext.c index d7396a8970e5..297e4cd8ce90 100644 --- a/mm/page_ext.c +++ b/mm/page_ext.c @@ -11,6 +11,7 @@ #include #include #include +#include /* * struct page extension @@ -89,6 +90,9 @@ static struct page_ext_operations *page_ext_ops[] __initdata = { #ifdef CONFIG_PAGE_TABLE_CHECK &page_table_check_ops, #endif +#ifdef CONFIG_IOMMU_DEBUG_PAGEALLOC + &page_iommu_debug_ops, +#endif }; unsigned long page_ext_size; -- 2.52.0.460.gd25c4c69ec-goog