From patchwork Wed Aug 11 20:36:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12431901 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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 52C79C4338F for ; Wed, 11 Aug 2021 20:36:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D05346101D for ; Wed, 11 Aug 2021 20:36:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D05346101D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 64E3A8D0003; Wed, 11 Aug 2021 16:36:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5FDE58D0001; Wed, 11 Aug 2021 16:36:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4C61A8D0003; Wed, 11 Aug 2021 16:36:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0238.hostedemail.com [216.40.44.238]) by kanga.kvack.org (Postfix) with ESMTP id 2D9548D0001 for ; Wed, 11 Aug 2021 16:36:32 -0400 (EDT) Received: from smtpin37.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id B960023E4D for ; Wed, 11 Aug 2021 20:36:31 +0000 (UTC) X-FDA: 78463957782.37.E4B8B00 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf26.hostedemail.com (Postfix) with ESMTP id 68B142016577 for ; Wed, 11 Aug 2021 20:36:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628714190; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bdoYRV/z4Dd8uSFdD6ay/3sfgEd/T31YzbcYRTGN8LA=; b=eahGDNHa6tAVfjkzRJ/QNB5OMdOY7IbTyrsZWnpYhbqqkHtvFaHJvygzcZ+7eUeaAeYUfj 3k5BSa8hjszkuuM3i1zCuHwms3Wri29qEEIj+Tu1lIG0z+qKT7ECbVD3fjdf1Th2aR4gJ9 ujQuUR8lHooRuqo3oicchpaRtqLVhzQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-460-zetTXEeyOXmFS2Sqm3pD5A-1; Wed, 11 Aug 2021 16:36:29 -0400 X-MC-Unique: zetTXEeyOXmFS2Sqm3pD5A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 346671082922; Wed, 11 Aug 2021 20:36:28 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.112]) by smtp.corp.redhat.com (Postfix) with ESMTP id 201861B46B; Wed, 11 Aug 2021 20:36:24 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , "Rafael J. Wysocki" , Andrew Morton , Dan Williams , Hanjun Guo , Andy Shevchenko , virtualization@lists.linux-foundation.org, linux-mm@kvack.org Subject: [PATCH v1 1/3] /dev/mem: disallow access to explicitly excluded system RAM regions Date: Wed, 11 Aug 2021 22:36:10 +0200 Message-Id: <20210811203612.138506-2-david@redhat.com> In-Reply-To: <20210811203612.138506-1-david@redhat.com> References: <20210811203612.138506-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Rspamd-Queue-Id: 68B142016577 Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=eahGDNHa; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf26.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=david@redhat.com X-Rspamd-Server: rspam04 X-Stat-Signature: 1w7d85iebmfspojijinnkuyg3qb7b3z4 X-HE-Tag: 1628714191-518870 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: virtio-mem dynamically exposes memory inside a device memory region as system RAM to Linux, coordinating with the hypervisor which parts are actually "plugged" and consequently usable/accessible. On the one hand, the virtio-mem driver adds/removes whole memory blocks, creating/removing busy IORESOURCE_SYSTEM_RAM resources, on the other hand, it logically (un)plugs memory inside added memory blocks, dynamically either exposing them to the buddy or hiding them from the buddy and marking them PG_offline. virtio-mem wants to make sure that in a sane environment, nobody "accidentially" accesses unplugged memory inside the device managed region. After /proc/kcore has been sanitized and /dev/kmem has been removed, /dev/mem is the remaining interface that still allows uncontrolled access to the device-managed region of virtio-mem devices from user space. There is no known sane use case for mapping virtio-mem device memory via /dev/mem while virtio-mem driver concurrently (un)plugs memory inside that region. So once the driver was loaded and detected the device along the device-managed region, we just want to disallow any access via /dev/mem to it. Let's add the basic infrastructure to exclude some physical memory regions completely from /dev/mem access, on any architecture and under any system configuration (independent of CONFIG_STRICT_DEVMEM and independent of "iomem="). Any range marked with "IORESOURCE_SYSTEM_RAM | IORESOURCE_EXCLUSIVE" will be excluded, even if not busy. For now, there are no applicable ranges and we'll modify virtio-mem next to properly set IORESOURCE_EXCLUSIVE on the parent resource. As next_resource() will iterate over children although we might want to skip a certain range completely, let's add and use next_range_skip_children() to optimize that case, avoding having to traverse subtrees that are not of interest. Signed-off-by: David Hildenbrand --- drivers/char/mem.c | 22 +++++++++------------- include/linux/ioport.h | 1 + kernel/resource.c | 42 ++++++++++++++++++++++++++++++++++++++++++ lib/Kconfig.debug | 4 +++- 4 files changed, 55 insertions(+), 14 deletions(-) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 1c596b5cdb27..bb6d95daab45 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -60,13 +60,18 @@ static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) } #endif -#ifdef CONFIG_STRICT_DEVMEM static inline int page_is_allowed(unsigned long pfn) { - return devmem_is_allowed(pfn); +#ifdef CONFIG_STRICT_DEVMEM + if (!devmem_is_allowed(pfn)) + return 0; +#endif /* CONFIG_STRICT_DEVMEM */ + return !iomem_range_contains_excluded(PFN_PHYS(pfn), PAGE_SIZE); } + static inline int range_is_allowed(unsigned long pfn, unsigned long size) { +#ifdef CONFIG_STRICT_DEVMEM u64 from = ((u64)pfn) << PAGE_SHIFT; u64 to = from + size; u64 cursor = from; @@ -77,18 +82,9 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size) cursor += PAGE_SIZE; pfn++; } - return 1; -} -#else -static inline int page_is_allowed(unsigned long pfn) -{ - return 1; -} -static inline int range_is_allowed(unsigned long pfn, unsigned long size) -{ - return 1; +#endif /* CONFIG_STRICT_DEVMEM */ + return !iomem_range_contains_excluded(PFN_PHYS(pfn), size); } -#endif #ifndef unxlate_dev_mem_ptr #define unxlate_dev_mem_ptr unxlate_dev_mem_ptr diff --git a/include/linux/ioport.h b/include/linux/ioport.h index 8359c50f9988..50523c28a5f1 100644 --- a/include/linux/ioport.h +++ b/include/linux/ioport.h @@ -308,6 +308,7 @@ extern struct resource * __devm_request_region(struct device *dev, extern void __devm_release_region(struct device *dev, struct resource *parent, resource_size_t start, resource_size_t n); extern int iomem_map_sanity_check(resource_size_t addr, unsigned long size); +extern bool iomem_range_contains_excluded(u64 addr, u64 size); extern bool iomem_is_exclusive(u64 addr); extern int diff --git a/kernel/resource.c b/kernel/resource.c index ca9f5198a01f..2938cf520ca3 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -73,6 +73,13 @@ static struct resource *next_resource(struct resource *p) return p->sibling; } +static struct resource *next_resource_skip_children(struct resource *p) +{ + while (!p->sibling && p->parent) + p = p->parent; + return p->sibling; +} + static void *r_next(struct seq_file *m, void *v, loff_t *pos) { struct resource *p = v; @@ -1700,6 +1707,41 @@ int iomem_map_sanity_check(resource_size_t addr, unsigned long size) return err; } +/* + * Check if a physical memory range is completely excluded from getting + * mapped/accessed via /dev/mem. + */ +bool iomem_range_contains_excluded(u64 addr, u64 size) +{ + const unsigned int flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_EXCLUSIVE; + bool excluded = false; + struct resource *p; + + read_lock(&resource_lock); + for (p = iomem_resource.child; p ;) { + if (p->start >= addr + size) + break; + if (p->end < addr) { + /* No need to consider children */ + p = next_resource_skip_children(p); + continue; + } + /* + * A system RAM resource is excluded if IORESOURCE_EXCLUSIVE + * is set, even if not busy and even if we don't have strict + * checks enabled -- no ifs or buts. + */ + if ((p->flags & flags) == flags) { + excluded = true; + break; + } + p = next_resource(p); + } + read_unlock(&resource_lock); + + return excluded; +} + #ifdef CONFIG_STRICT_DEVMEM static int strict_iomem_checks = 1; #else diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 5ddd575159fb..d0ce6e23a6db 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1780,7 +1780,9 @@ config STRICT_DEVMEM access to this is obviously disastrous, but specific access can be used by people debugging the kernel. Note that with PAT support enabled, even in this case there are restrictions on /dev/mem - use due to the cache aliasing requirements. + use due to the cache aliasing requirements. Further, some drivers + will still restrict access to some physical memory regions either + already used or to be used in the future as system RAM. If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem file only allows userspace access to PCI space and the BIOS code and