From patchwork Fri May 28 01:04:15 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Collingbourne X-Patchwork-Id: 12285969 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=-17.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_ADSP_CUSTOM_MED,DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 F290DC47089 for ; Fri, 28 May 2021 01:15:27 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id B065561183 for ; Fri, 28 May 2021 01:15:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B065561183 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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:Cc:To:From:Subject:References: Mime-Version:Message-Id:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=5O58/MvC5dlIZa+JjqnSw3PS5/uTcEuDQwjZ8TMY/6c=; b=eu6pBBedfP7jqWg2nv+bz2pMll O7EhWBuZQB9+Uf6uaNTaVkcL+H0p3iD0xOTueeth2O3L2ZBczmn2TKYYS7LUi8KY7EI5I/iLX5+5P xCwMK0z66IrDXy7J9SAgjHAg+hkcMhT5E2VirDUH4WQYPSU2gRNQ5EAkhtfTPvwLjeOsqW5fvVuO0 xhrNCmb5N86YpRuZfe5txYmE4G2Xyy4Vl6677XrakKv6n1lyWUKVsadrOxIOztu0Q6d2bAfjL/UJC V17TMJdg/VItlf8fNRvM6QjfqnjPS1UsdliP4tE3MH3cc56zz3hVX+h9Ew/L3p9vlMZeqtOhm7M22 xjMwCuNQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lmR3v-00Aqxc-C8; Fri, 28 May 2021 01:13:21 +0000 Received: from mail-yb1-xb4a.google.com ([2607:f8b0:4864:20::b4a]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lmQvi-00Anq5-7v for linux-arm-kernel@lists.infradead.org; Fri, 28 May 2021 01:04:53 +0000 Received: by mail-yb1-xb4a.google.com with SMTP id s8-20020a5b04480000b029049fb35700b9so2525970ybp.5 for ; Thu, 27 May 2021 18:04:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=bvjOAU6fZM7OANZ2gg3RMz5WHamI05sKrzERatXfroY=; b=MkdMq0fD1SyBlroVkc/5qCTbKp7mNIRS2K/Fk2sJGu9Z9gNR/ehqq7XUbUWfw+HrT0 j59c37ussmppNsC0cQHJJ76/GBRGS4wn6xeQX6t7+DOWvrRdUkpwjdljAvxOzrVb6vFY eHA5b0SGqMK9+JZzhHufWv8Rw2SSZuX+F7TcI0CTGBg34fHILMa8Pepyd63q/KzJZYD7 HR/ZZKE7HrYE/VrvMg7V6V9zDYLt0tFZzPMy23ouKJLtnu83E3X/GevLPUvju6qt2tt9 OCYbr2NGBNhmLZQFvc8JDjZYmzZq9zmkprP1ANfnhAIH4LDj/td9PVwkc+HzT1vail7d soPQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=bvjOAU6fZM7OANZ2gg3RMz5WHamI05sKrzERatXfroY=; b=bI2gO6zG1R8LcErm1z+aBpa5/aR8M0MdqkciZxoWDkpMGNx0gECGMZZPlCmwW8n7l+ YIGApqm4T6qw9lb4LG2g12WCD6c1Sbo4a3oFTTZJ+lmF47MZ4xJTpu8wqLUXMD4cdpvr 1iUYYeu+Q4Ft2bM04MzC+a313eXDFYMMFcNAdLf5JUgEe0kcWPP0mtruclkCJMmpwUAt Sf3Lrrl2IL+X+GTvtArzNfCyLbsG6owXe4Q7dqg7+tGuq0AGURJqsSe/maq31KOsETII RwfwbVwBUuMH+MmdMkc2JWKQvJ7FCkbOdpEZzXThi1OqED7tyOQc5y84cC6fuuK4qe2+ djXw== X-Gm-Message-State: AOAM530j6XG0KYrUk+KEQEC6yqym9QOf7/+UdcydD5ybMhsObh5S7Mek M0GI5Mohx3R6o8wo/mj5DwCTn1o= X-Google-Smtp-Source: ABdhPJxnYsgoFIburpsNg3/KGgbah5a5lw2FRiSFhWc7Yi2AWVTplFXDDy//azzGJPRavYaK380oasg= X-Received: from pcc-desktop.svl.corp.google.com ([2620:15c:2ce:200:81d5:efb9:ec22:d557]) (user=pcc job=sendgmr) by 2002:a25:7cc2:: with SMTP id x185mr8880333ybc.216.1622163888255; Thu, 27 May 2021 18:04:48 -0700 (PDT) Date: Thu, 27 May 2021 18:04:15 -0700 In-Reply-To: <20210528010415.1852012-1-pcc@google.com> Message-Id: <20210528010415.1852012-5-pcc@google.com> Mime-Version: 1.0 References: <20210528010415.1852012-1-pcc@google.com> X-Mailer: git-send-email 2.32.0.rc0.204.g9fa02ecfa5-goog Subject: [PATCH v4 4/4] kasan: disable freed user page poisoning with HW tags From: Peter Collingbourne To: Andrey Konovalov , Alexander Potapenko , Catalin Marinas , Vincenzo Frascino , Andrew Morton , Jann Horn Cc: Peter Collingbourne , Evgenii Stepanov , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210527_180450_353779_890C3EB2 X-CRM114-Status: GOOD ( 20.38 ) 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 Poisoning freed pages protects against kernel use-after-free. The likelihood of such a bug involving kernel pages is significantly higher than that for user pages. At the same time, poisoning freed pages can impose a significant performance cost, which cannot always be justified for user pages given the lower probability of finding a bug. Therefore, disable freed user page poisoning when using HW tags. We identify "user" pages via the flag set GFP_HIGHUSER_MOVABLE, which indicates a strong likelihood of not being directly accessible to the kernel. Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/I716846e2de8ef179f44e835770df7e6307be96c9 --- v4: - move flag to GFP_HIGHUSER_MOVABLE - remove command line flag include/linux/gfp.h | 13 ++++++++++--- include/linux/page-flags.h | 9 +++++++++ include/trace/events/mmflags.h | 9 ++++++++- mm/kasan/hw_tags.c | 3 +++ mm/page_alloc.c | 12 +++++++----- 5 files changed, 37 insertions(+), 9 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 68ba237365dc..e6102dfa4faa 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -54,8 +54,9 @@ struct vm_area_struct; #define ___GFP_THISNODE 0x200000u #define ___GFP_ACCOUNT 0x400000u #define ___GFP_ZEROTAGS 0x800000u +#define ___GFP_SKIP_KASAN_POISON 0x1000000u #ifdef CONFIG_LOCKDEP -#define ___GFP_NOLOCKDEP 0x1000000u +#define ___GFP_NOLOCKDEP 0x2000000u #else #define ___GFP_NOLOCKDEP 0 #endif @@ -233,17 +234,22 @@ struct vm_area_struct; * * %__GFP_ZEROTAGS returns a page with zeroed memory tags on success, if * __GFP_ZERO is set. + * + * %__GFP_SKIP_KASAN_POISON returns a page which does not need to be poisoned + * on deallocation. Typically used for userspace pages. Currently only has an + * effect in HW tags mode. */ #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) #define __GFP_COMP ((__force gfp_t)___GFP_COMP) #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) #define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS) +#define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON) /* Disable lockdep for GFP context tracking */ #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) /* Room for N __GFP_FOO bits */ -#define __GFP_BITS_SHIFT (24 + IS_ENABLED(CONFIG_LOCKDEP)) +#define __GFP_BITS_SHIFT (25 + IS_ENABLED(CONFIG_LOCKDEP)) #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) /** @@ -324,7 +330,8 @@ struct vm_area_struct; #define GFP_DMA __GFP_DMA #define GFP_DMA32 __GFP_DMA32 #define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM) -#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE) +#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | \ + __GFP_SKIP_KASAN_POISON) #define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \ __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM) #define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 04a34c08e0a6..40e2c5000585 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -137,6 +137,9 @@ enum pageflags { #endif #ifdef CONFIG_64BIT PG_arch_2, +#endif +#ifdef CONFIG_KASAN_HW_TAGS + PG_skip_kasan_poison, #endif __NR_PAGEFLAGS, @@ -443,6 +446,12 @@ TESTCLEARFLAG(Young, young, PF_ANY) PAGEFLAG(Idle, idle, PF_ANY) #endif +#ifdef CONFIG_KASAN_HW_TAGS +PAGEFLAG(SkipKASanPoison, skip_kasan_poison, PF_HEAD) +#else +PAGEFLAG_FALSE(SkipKASanPoison) +#endif + /* * PageReported() is used to track reported free pages within the Buddy * allocator. We can use the non-atomic version of the test and set diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h index 629c7a0eaff2..390270e00a1d 100644 --- a/include/trace/events/mmflags.h +++ b/include/trace/events/mmflags.h @@ -85,6 +85,12 @@ #define IF_HAVE_PG_ARCH_2(flag,string) #endif +#ifdef CONFIG_KASAN_HW_TAGS +#define IF_HAVE_PG_SKIP_KASAN_POISON(flag,string) ,{1UL << flag, string} +#else +#define IF_HAVE_PG_SKIP_KASAN_POISON(flag,string) +#endif + #define __def_pageflag_names \ {1UL << PG_locked, "locked" }, \ {1UL << PG_waiters, "waiters" }, \ @@ -112,7 +118,8 @@ IF_HAVE_PG_UNCACHED(PG_uncached, "uncached" ) \ IF_HAVE_PG_HWPOISON(PG_hwpoison, "hwpoison" ) \ IF_HAVE_PG_IDLE(PG_young, "young" ) \ IF_HAVE_PG_IDLE(PG_idle, "idle" ) \ -IF_HAVE_PG_ARCH_2(PG_arch_2, "arch_2" ) +IF_HAVE_PG_ARCH_2(PG_arch_2, "arch_2" ) \ +IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison") #define show_page_flags(flags) \ (flags) ? __print_flags(flags, "|", \ diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 41fd5326ee0a..ed5e5b833d61 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -246,6 +246,9 @@ void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags) */ bool init = !want_init_on_free() && want_init_on_alloc(flags); + if (flags & __GFP_SKIP_KASAN_POISON) + SetPageSkipKASanPoison(page); + if (flags & __GFP_ZEROTAGS) { int i; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 13937e793fda..5ad76e540a22 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -394,11 +394,12 @@ static DEFINE_STATIC_KEY_TRUE(deferred_pages); * on-demand allocation and then freed again before the deferred pages * initialization is done, but this is not likely to happen. */ -static inline bool should_skip_kasan_poison(fpi_t fpi_flags) +static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags) { return static_branch_unlikely(&deferred_pages) || (!IS_ENABLED(CONFIG_KASAN_GENERIC) && - (fpi_flags & FPI_SKIP_KASAN_POISON)); + (fpi_flags & FPI_SKIP_KASAN_POISON)) || + PageSkipKASanPoison(page); } /* Returns true if the struct page for the pfn is uninitialised */ @@ -449,10 +450,11 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn) return false; } #else -static inline bool should_skip_kasan_poison(fpi_t fpi_flags) +static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags) { return (!IS_ENABLED(CONFIG_KASAN_GENERIC) && - (fpi_flags & FPI_SKIP_KASAN_POISON)); + (fpi_flags & FPI_SKIP_KASAN_POISON)) || + PageSkipKASanPoison(page); } static inline bool early_page_uninitialised(unsigned long pfn) @@ -1244,7 +1246,7 @@ static __always_inline bool free_pages_prepare(struct page *page, unsigned int order, bool check_free, fpi_t fpi_flags) { int bad = 0; - bool skip_kasan_poison = should_skip_kasan_poison(fpi_flags); + bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags); VM_BUG_ON_PAGE(PageTail(page), page);