From patchwork Mon Dec 20 22:02:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: andrey.konovalov@linux.dev X-Patchwork-Id: 12696937 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7FC29C433F5 for ; Mon, 20 Dec 2021 22:20:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=BeNXeBtZPVlk2QgdNR7AyqHyPUf3Q9XYOIPOpppTLIg=; b=1qHL+9SdtdgXQ/ +7ATIWtHCGUtTWT+c2I96dN+lzvF2+SnhmnabX1riqtfIOLWW8N7SnZWgs8a402p+pKVqigsUuLUM EuZwTqTfwKsQn3uePLhXysSZjLCQJBfnH8/jqp4FFyZZ55RNCWjIPBcuU58OOtIYbzhdv3loE7IXO 3LkOEaSbRj/nALzyO3nM8gNNnswv2AG+Wp7U3Mkjm4dHdmxVKI0ZDqzQdIgw8nrZ1By0GO8TeMlGV +rRHQK5PmJjkQy7Oy9Av3QUrrs+W1A/bmwrvbase1RSUAIU6EHxht/IuXb7rYyjioQ4eaPIvaXMHO Y2LUmw/v3PCO8X3N5gHg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mzR08-004les-Mq; Mon, 20 Dec 2021 22:19:25 +0000 Received: from out1.migadu.com ([2001:41d0:2:863f::]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mzQjh-004ciw-M9 for linux-arm-kernel@lists.infradead.org; Mon, 20 Dec 2021 22:02:28 +0000 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1640037744; 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=kur2ASckBTfMXx5vBveod/WRZYhkEYj/b8Zk+mLRv7w=; b=Hun8KCBY8jSj6ILBfgvgHL4ixG2of4JNKkkfTDpsPF9WvUIHQXMQEDqqozcULeSBNi+/lt IsJjR0+4Zxxiun5qhMGG6/HucPU90SevwTiO8dj2YzbrPfB8VRJBnZf6Qc/wpycSi+isF+ +cKgf/E9qW4NaWtbFNJkVlu2cjFgNJw= From: andrey.konovalov@linux.dev To: Marco Elver , Alexander Potapenko , Andrew Morton Cc: Andrey Konovalov , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, linux-mm@kvack.org, Vincenzo Frascino , Catalin Marinas , Will Deacon , Mark Rutland , linux-arm-kernel@lists.infradead.org, Peter Collingbourne , Evgenii Stepanov , linux-kernel@vger.kernel.org, Andrey Konovalov Subject: [PATCH mm v4 31/39] kasan, vmalloc: only tag normal vmalloc allocations Date: Mon, 20 Dec 2021 23:02:03 +0100 Message-Id: <09fc776d03e8aaa9efa78c743392972060f5256d.1640036051.git.andreyknvl@google.com> In-Reply-To: References: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211220_140226_135486_652BD725 X-CRM114-Status: GOOD ( 20.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Andrey Konovalov The kernel can use to allocate executable memory. The only supported way to do that is via __vmalloc_node_range() with the executable bit set in the prot argument. (vmap() resets the bit via pgprot_nx()). Once tag-based KASAN modes start tagging vmalloc allocations, executing code from such allocations will lead to the PC register getting a tag, which is not tolerated by the kernel. Only tag the allocations for normal kernel pages. Signed-off-by: Andrey Konovalov --- Changes v3->v4: - Rename KASAN_VMALLOC_NOEXEC to KASAN_VMALLOC_PROT_NORMAL. - Compare with PAGE_KERNEL instead of using pgprot_nx(). - Update patch description. Changes v2->v3: - Add this patch. --- include/linux/kasan.h | 7 ++++--- mm/kasan/hw_tags.c | 7 +++++++ mm/kasan/shadow.c | 7 +++++++ mm/vmalloc.c | 49 +++++++++++++++++++++++++------------------ 4 files changed, 47 insertions(+), 23 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 499f1573dba4..3593c95d1fa5 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -27,9 +27,10 @@ struct kunit_kasan_expectation { typedef unsigned int __bitwise kasan_vmalloc_flags_t; -#define KASAN_VMALLOC_NONE 0x00u -#define KASAN_VMALLOC_INIT 0x01u -#define KASAN_VMALLOC_VM_ALLOC 0x02u +#define KASAN_VMALLOC_NONE 0x00u +#define KASAN_VMALLOC_INIT 0x01u +#define KASAN_VMALLOC_VM_ALLOC 0x02u +#define KASAN_VMALLOC_PROT_NORMAL 0x04u #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 21104fd51872..2e9378a4f07f 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -247,6 +247,13 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, if (!(flags & KASAN_VMALLOC_VM_ALLOC)) return (void *)start; + /* + * Don't tag executable memory. + * The kernel doesn't tolerate having the PC register tagged. + */ + if (!(flags & KASAN_VMALLOC_PROT_NORMAL)) + return (void *)start; + tag = kasan_random_tag(); start = set_tag(start, tag); diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index b958babc8fed..7272e248db87 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -488,6 +488,13 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, if (!is_vmalloc_or_module_addr(start)) return (void *)start; + /* + * Don't tag executable memory. + * The kernel doesn't tolerate having the PC register tagged. + */ + if (!(flags & KASAN_VMALLOC_PROT_NORMAL)) + return (void *)start; + start = set_tag(start, kasan_random_tag()); kasan_unpoison(start, size, false); return (void *)start; diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 47f3de7a3396..01ec2ef447af 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2220,7 +2220,7 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node) * With hardware tag-based KASAN, marking is skipped for * non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc(). */ - mem = kasan_unpoison_vmalloc(mem, size, KASAN_VMALLOC_NONE); + mem = kasan_unpoison_vmalloc(mem, size, KASAN_VMALLOC_PROT_NORMAL); return mem; } @@ -2459,7 +2459,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size, */ if (!(flags & VM_ALLOC)) area->addr = kasan_unpoison_vmalloc(area->addr, requested_size, - KASAN_VMALLOC_NONE); + KASAN_VMALLOC_PROT_NORMAL); return area; } @@ -3065,7 +3065,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, { struct vm_struct *area; void *ret; - kasan_vmalloc_flags_t kasan_flags; + kasan_vmalloc_flags_t kasan_flags = KASAN_VMALLOC_NONE; unsigned long real_size = size; unsigned long real_align = align; unsigned int shift = PAGE_SHIFT; @@ -3118,21 +3118,28 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, goto fail; } - /* Prepare arguments for __vmalloc_area_node(). */ - if (kasan_hw_tags_enabled() && - pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) { - /* - * Modify protection bits to allow tagging. - * This must be done before mapping in __vmalloc_area_node(). - */ - prot = arch_vmap_pgprot_tagged(prot); + /* + * Prepare arguments for __vmalloc_area_node() and + * kasan_unpoison_vmalloc(). + */ + if (pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) { + if (kasan_hw_tags_enabled()) { + /* + * Modify protection bits to allow tagging. + * This must be done before mapping. + */ + prot = arch_vmap_pgprot_tagged(prot); - /* - * Skip page_alloc poisoning and zeroing for physical pages - * backing VM_ALLOC mapping. Memory is instead poisoned and - * zeroed by kasan_unpoison_vmalloc(). - */ - gfp_mask |= __GFP_SKIP_KASAN_UNPOISON | __GFP_SKIP_ZERO; + /* + * Skip page_alloc poisoning and zeroing for physical + * pages backing VM_ALLOC mapping. Memory is instead + * poisoned and zeroed by kasan_unpoison_vmalloc(). + */ + gfp_mask |= __GFP_SKIP_KASAN_UNPOISON | __GFP_SKIP_ZERO; + } + + /* Take note that the mapping is PAGE_KERNEL. */ + kasan_flags |= KASAN_VMALLOC_PROT_NORMAL; } /* Allocate physical pages and map them into vmalloc space. */ @@ -3146,10 +3153,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, * (except for the should_skip_init() check) to make sure that memory * is initialized under the same conditions regardless of the enabled * KASAN mode. + * Tag-based KASAN modes only assign tags to normal non-executable + * allocations, see __kasan_unpoison_vmalloc(). */ - kasan_flags = KASAN_VMALLOC_VM_ALLOC; + kasan_flags |= KASAN_VMALLOC_VM_ALLOC; if (!want_init_on_free() && want_init_on_alloc(gfp_mask)) kasan_flags |= KASAN_VMALLOC_INIT; + /* KASAN_VMALLOC_PROT_NORMAL already set if required. */ area->addr = kasan_unpoison_vmalloc(area->addr, real_size, kasan_flags); /* @@ -3863,8 +3873,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, */ for (area = 0; area < nr_vms; area++) vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr, - vms[area]->size, - KASAN_VMALLOC_NONE); + vms[area]->size, KASAN_VMALLOC_PROT_NORMAL); kfree(vas); return vms;