From patchwork Thu Jun 27 13:03:15 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Potapenko X-Patchwork-Id: 11019697 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4B75A1580 for ; Thu, 27 Jun 2019 13:05:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3D5C228B13 for ; Thu, 27 Jun 2019 13:05:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3167728B11; Thu, 27 Jun 2019 13:05:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id D9BFB28A13 for ; Thu, 27 Jun 2019 13:05:22 +0000 (UTC) Received: (qmail 28455 invoked by uid 550); 27 Jun 2019 13:05:17 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Delivered-To: moderator for kernel-hardening@lists.openwall.com Received: (qmail 26142 invoked from network); 27 Jun 2019 13:03:40 -0000 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=DwC5p+kwOXGC6Ndr/JfB7BzEJ0LkGdtCDOkPBoQxauU=; b=r4hVtpczFWR9WFuiUmI0jx7dPToY8E7M5M3uTFXDqiFisYIhTn0gSIQMNCRuPfpdvk z4j43Ptbx0CAtSQWSYx/yBf4R/OZBkHHjUAgwOj2EcaoSnLT2m4uAAGQi+HxH4yYlYyE 9z9lin7sIUxLRlko98cFqgWN3B798yB23Yt0vsxliDWPuasB20BNB9qfSUDo2T2JznND I4AU5bt9UdVoqEAXoyOHOU9XDbp/UycmdfvY0LFzDIkX3iyxUlHgNu6JzFhj7LtaP6g8 kjTKiUA0B1taMfMLl+gZz5Ys4KBFUHB5Yb9qQ65ZiybdNSpqWtVAeOHLOAprS4fZyz7F Hv+g== 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=DwC5p+kwOXGC6Ndr/JfB7BzEJ0LkGdtCDOkPBoQxauU=; b=DQy/6plbUA60jgoni95dfzJ1I/J4fPTNzrouY0wozLTmnkLepe6SPggU/MgK3iOvET oEqXYG6d/c0oCo5OigqOMix+YHyL7faVFArBZubs+u1dr8f5gqrsCriI6rf5Pw/+0USV BrlWHivnep5GaGBFWNU+AV+i12Qr7pGhdPbi/Ih8+k7aVz/+XGcqEhCZn4XEl7eyzJXg 818uFnFNZwXZxNWyFU+RvLL75bhgDpnsVps8PmYFnE720xlDbF8E5yog+L2v/fefzRjC zbdCv7Nkn4t0UWDk0bHqb5/pgvjfAGbU95auaswKB4at3/QLDDc8Q22bdClzzqovGFk9 zJYQ== X-Gm-Message-State: APjAAAW8HjtcB4dXXEzebga6G4r1FskhqHPJ0HpbxUn7lh6662FHoTVr DrDRM7vngoKLbL3RBfeiYaXTQvjhrVA= X-Google-Smtp-Source: APXvYqzqmWjGWWOH/WQf8m9WyzP/GQw4iQWoVAYap6Kh7hgXtFIxPIoo/UVcsPLoAFMSNb2cysPzfrge5PQ= X-Received: by 2002:a1f:62c3:: with SMTP id w186mr1298739vkb.82.1561640608011; Thu, 27 Jun 2019 06:03:28 -0700 (PDT) Date: Thu, 27 Jun 2019 15:03:15 +0200 In-Reply-To: <20190627130316.254309-1-glider@google.com> Message-Id: <20190627130316.254309-2-glider@google.com> Mime-Version: 1.0 References: <20190627130316.254309-1-glider@google.com> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog Subject: [PATCH v9 1/2] mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options From: Alexander Potapenko To: Andrew Morton , Christoph Lameter , Kees Cook Cc: Alexander Potapenko , Masahiro Yamada , Michal Hocko , James Morris , "Serge E. Hallyn" , Nick Desaulniers , Kostya Serebryany , Dmitry Vyukov , Sandeep Patil , Laura Abbott , Randy Dunlap , Jann Horn , Mark Rutland , Marco Elver , Qian Cai , linux-mm@kvack.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com X-Virus-Scanned: ClamAV using ClamSMTP The new options are needed to prevent possible information leaks and make control-flow bugs that depend on uninitialized values more deterministic. This is expected to be on-by-default on Android and Chrome OS. And it gives the opportunity for anyone else to use it under distros too via the boot args. (The init_on_free feature is regularly requested by folks where memory forensics is included in their threat models.) init_on_alloc=1 makes the kernel initialize newly allocated pages and heap objects with zeroes. Initialization is done at allocation time at the places where checks for __GFP_ZERO are performed. init_on_free=1 makes the kernel initialize freed pages and heap objects with zeroes upon their deletion. This helps to ensure sensitive data doesn't leak via use-after-free accesses. Both init_on_alloc=1 and init_on_free=1 guarantee that the allocator returns zeroed memory. The two exceptions are slab caches with constructors and SLAB_TYPESAFE_BY_RCU flag. Those are never zero-initialized to preserve their semantics. Both init_on_alloc and init_on_free default to zero, but those defaults can be overridden with CONFIG_INIT_ON_ALLOC_DEFAULT_ON and CONFIG_INIT_ON_FREE_DEFAULT_ON. If either SLUB poisoning or page poisoning is enabled, those options take precedence over init_on_alloc and init_on_free: initialization is only applied to unpoisoned allocations. Slowdown for the new features compared to init_on_free=0, init_on_alloc=0: hackbench, init_on_free=1: +7.62% sys time (st.err 0.74%) hackbench, init_on_alloc=1: +7.75% sys time (st.err 2.14%) Linux build with -j12, init_on_free=1: +8.38% wall time (st.err 0.39%) Linux build with -j12, init_on_free=1: +24.42% sys time (st.err 0.52%) Linux build with -j12, init_on_alloc=1: -0.13% wall time (st.err 0.42%) Linux build with -j12, init_on_alloc=1: +0.57% sys time (st.err 0.40%) The slowdown for init_on_free=0, init_on_alloc=0 compared to the baseline is within the standard error. The new features are also going to pave the way for hardware memory tagging (e.g. arm64's MTE), which will require both on_alloc and on_free hooks to set the tags for heap objects. With MTE, tagging will have the same cost as memory initialization. Although init_on_free is rather costly, there are paranoid use-cases where in-memory data lifetime is desired to be minimized. There are various arguments for/against the realism of the associated threat models, but given that we'll need the infrastructure for MTE anyway, and there are people who want wipe-on-free behavior no matter what the performance cost, it seems reasonable to include it in this series. Signed-off-by: Alexander Potapenko Acked-by: Kees Cook To: Andrew Morton To: Christoph Lameter To: Kees Cook Cc: Masahiro Yamada Cc: Michal Hocko Cc: James Morris Cc: "Serge E. Hallyn" Cc: Nick Desaulniers Cc: Kostya Serebryany Cc: Dmitry Vyukov Cc: Sandeep Patil Cc: Laura Abbott Cc: Randy Dunlap Cc: Jann Horn Cc: Mark Rutland Cc: Marco Elver Cc: Qian Cai Cc: linux-mm@kvack.org Cc: linux-security-module@vger.kernel.org Cc: kernel-hardening@lists.openwall.com Signed-off-by: Andrew Morton Acked-by: Michal Hocko # page and dmapool parts Acked-by: James Morris --- v2: - unconditionally initialize pages in kernel_init_free_pages() - comment from Randy Dunlap: drop 'default false' lines from Kconfig.hardening v3: - don't call kernel_init_free_pages() from memblock_free_pages() - adopted some Kees' comments for the patch description v4: - use NULL instead of 0 in slab_alloc_node() (found by kbuild test robot) - don't write to NULL object in slab_alloc_node() (found by Android testing) v5: - adjusted documentation wording as suggested by Kees - disable SLAB_POISON if auto-initialization is on - don't wipe RCU cache allocations made without __GFP_ZERO - dropped SLOB support v7: - rebase the patch, added the Acked-by: tag v8: - addressed comments by Michal Hocko: revert kernel/kexec_core.c and apply initialization in dma_pool_free() - disable init_on_alloc/init_on_free if slab poisoning or page poisoning are enabled, as requested by Qian Cai - skip the redzone when initializing a freed heap object, as requested by Qian Cai and Kees Cook - use s->offset to address the freeptr (suggested by Kees Cook) - updated the patch description, added Signed-off-by: tag v9: - picked up -mm fixes from Qian Cai and Andrew Morton (order of calls in free_pages_prepare(), export init_on_alloc) - exported init_on_free - allowed using init_on_alloc/init_on_free with SLUB poisoning and page poisoning. Poisoning supersedes zero-initialization, so some tests may behave differently with poisoning enabled. --- .../admin-guide/kernel-parameters.txt | 9 +++ drivers/infiniband/core/uverbs_ioctl.c | 2 +- include/linux/mm.h | 24 +++++++ mm/dmapool.c | 4 +- mm/page_alloc.c | 71 +++++++++++++++++-- mm/slab.c | 16 ++++- mm/slab.h | 20 ++++++ mm/slub.c | 41 +++++++++-- net/core/sock.c | 2 +- security/Kconfig.hardening | 29 ++++++++ 10 files changed, 200 insertions(+), 18 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 138f6664b2e2..84ee1121a2b9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1673,6 +1673,15 @@ initrd= [BOOT] Specify the location of the initial ramdisk + init_on_alloc= [MM] Fill newly allocated pages and heap objects with + zeroes. + Format: 0 | 1 + Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. + + init_on_free= [MM] Fill freed pages and heap objects with zeroes. + Format: 0 | 1 + Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. + init_pkru= [x86] Specify the default memory protection keys rights register contents for all processes. 0x55555554 by default (disallow access to all but pkey 0). Can diff --git a/drivers/infiniband/core/uverbs_ioctl.c b/drivers/infiniband/core/uverbs_ioctl.c index 829b0c6944d8..61758201d9b2 100644 --- a/drivers/infiniband/core/uverbs_ioctl.c +++ b/drivers/infiniband/core/uverbs_ioctl.c @@ -127,7 +127,7 @@ __malloc void *_uverbs_alloc(struct uverbs_attr_bundle *bundle, size_t size, res = (void *)pbundle->internal_buffer + pbundle->internal_used; pbundle->internal_used = ALIGN(new_used, sizeof(*pbundle->internal_buffer)); - if (flags & __GFP_ZERO) + if (want_init_on_alloc(flags)) memset(res, 0, size); return res; } diff --git a/include/linux/mm.h b/include/linux/mm.h index dd0b5f4e1e45..81b582657854 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2696,6 +2696,30 @@ static inline void kernel_poison_pages(struct page *page, int numpages, int enable) { } #endif +#ifdef CONFIG_INIT_ON_ALLOC_DEFAULT_ON +DECLARE_STATIC_KEY_TRUE(init_on_alloc); +#else +DECLARE_STATIC_KEY_FALSE(init_on_alloc); +#endif +static inline bool want_init_on_alloc(gfp_t flags) +{ + if (static_branch_unlikely(&init_on_alloc) && + !page_poisoning_enabled()) + return true; + return flags & __GFP_ZERO; +} + +#ifdef CONFIG_INIT_ON_FREE_DEFAULT_ON +DECLARE_STATIC_KEY_TRUE(init_on_free); +#else +DECLARE_STATIC_KEY_FALSE(init_on_free); +#endif +static inline bool want_init_on_free(void) +{ + return static_branch_unlikely(&init_on_free) && + !page_poisoning_enabled(); +} + extern bool _debug_pagealloc_enabled; static inline bool debug_pagealloc_enabled(void) diff --git a/mm/dmapool.c b/mm/dmapool.c index 8c94c89a6f7e..fe5d33060415 100644 --- a/mm/dmapool.c +++ b/mm/dmapool.c @@ -378,7 +378,7 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags, #endif spin_unlock_irqrestore(&pool->lock, flags); - if (mem_flags & __GFP_ZERO) + if (want_init_on_alloc(mem_flags)) memset(retval, 0, pool->size); return retval; @@ -428,6 +428,8 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma) } offset = vaddr - page->vaddr; + if (want_init_on_free()) + memset(vaddr, 0, pool->size); #ifdef DMAPOOL_DEBUG if ((dma - page->dma) != offset) { spin_unlock_irqrestore(&pool->lock, flags); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d66bc8abe0af..c3123fa41bba 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -136,6 +136,55 @@ unsigned long totalcma_pages __read_mostly; int percpu_pagelist_fraction; gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK; +#ifdef CONFIG_INIT_ON_ALLOC_DEFAULT_ON +DEFINE_STATIC_KEY_TRUE(init_on_alloc); +#else +DEFINE_STATIC_KEY_FALSE(init_on_alloc); +#endif +EXPORT_SYMBOL(init_on_alloc); + +#ifdef CONFIG_INIT_ON_FREE_DEFAULT_ON +DEFINE_STATIC_KEY_TRUE(init_on_free); +#else +DEFINE_STATIC_KEY_FALSE(init_on_free); +#endif +EXPORT_SYMBOL(init_on_free); + +static int __init early_init_on_alloc(char *buf) +{ + int ret; + bool bool_result; + + if (!buf) + return -EINVAL; + ret = kstrtobool(buf, &bool_result); + if (bool_result && IS_ENABLED(CONFIG_PAGE_POISONING)) + pr_warn("mem auto-init: CONFIG_PAGE_POISONING is on, will take precedence over init_on_alloc\n"); + if (bool_result) + static_branch_enable(&init_on_alloc); + else + static_branch_disable(&init_on_alloc); + return ret; +} +early_param("init_on_alloc", early_init_on_alloc); + +static int __init early_init_on_free(char *buf) +{ + int ret; + bool bool_result; + + if (!buf) + return -EINVAL; + ret = kstrtobool(buf, &bool_result); + if (bool_result && IS_ENABLED(CONFIG_PAGE_POISONING)) + pr_warn("mem auto-init: CONFIG_PAGE_POISONING is on, will take precedence over init_on_free\n"); + if (bool_result) + static_branch_enable(&init_on_free); + else + static_branch_disable(&init_on_free); + return ret; +} +early_param("init_on_free", early_init_on_free); /* * A cached value of the page's pageblock's migratetype, used when the page is @@ -1090,6 +1139,14 @@ static int free_tail_pages_check(struct page *head_page, struct page *page) return ret; } +static void kernel_init_free_pages(struct page *page, int numpages) +{ + int i; + + for (i = 0; i < numpages; i++) + clear_highpage(page + i); +} + static __always_inline bool free_pages_prepare(struct page *page, unsigned int order, bool check_free) { @@ -1141,6 +1198,9 @@ static __always_inline bool free_pages_prepare(struct page *page, PAGE_SIZE << order); } arch_free_page(page, order); + if (want_init_on_free()) + kernel_init_free_pages(page, 1 << order); + kernel_poison_pages(page, 1 << order, 0); if (debug_pagealloc_enabled()) kernel_map_pages(page, 1 << order, 0); @@ -2020,8 +2080,8 @@ static inline int check_new_page(struct page *page) static inline bool free_pages_prezeroed(void) { - return IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) && - page_poisoning_enabled(); + return (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) && + page_poisoning_enabled()) || want_init_on_free(); } #ifdef CONFIG_DEBUG_VM @@ -2075,13 +2135,10 @@ inline void post_alloc_hook(struct page *page, unsigned int order, static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, unsigned int alloc_flags) { - int i; - post_alloc_hook(page, order, gfp_flags); - if (!free_pages_prezeroed() && (gfp_flags & __GFP_ZERO)) - for (i = 0; i < (1 << order); i++) - clear_highpage(page + i); + if (!free_pages_prezeroed() && want_init_on_alloc(gfp_flags)) + kernel_init_free_pages(page, 1 << order); if (order && (gfp_flags & __GFP_COMP)) prep_compound_page(page, order); diff --git a/mm/slab.c b/mm/slab.c index f7117ad9b3a3..98a89d7c922d 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1830,6 +1830,14 @@ static bool set_objfreelist_slab_cache(struct kmem_cache *cachep, cachep->num = 0; + /* + * If slab auto-initialization on free is enabled, store the freelist + * off-slab, so that its contents don't end up in one of the allocated + * objects. + */ + if (unlikely(slab_want_init_on_free(cachep))) + return false; + if (cachep->ctor || flags & SLAB_TYPESAFE_BY_RCU) return false; @@ -3263,7 +3271,7 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid, local_irq_restore(save_flags); ptr = cache_alloc_debugcheck_after(cachep, flags, ptr, caller); - if (unlikely(flags & __GFP_ZERO) && ptr) + if (unlikely(slab_want_init_on_alloc(flags, cachep)) && ptr) memset(ptr, 0, cachep->object_size); slab_post_alloc_hook(cachep, flags, 1, &ptr); @@ -3320,7 +3328,7 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller) objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller); prefetchw(objp); - if (unlikely(flags & __GFP_ZERO) && objp) + if (unlikely(slab_want_init_on_alloc(flags, cachep)) && objp) memset(objp, 0, cachep->object_size); slab_post_alloc_hook(cachep, flags, 1, &objp); @@ -3441,6 +3449,8 @@ void ___cache_free(struct kmem_cache *cachep, void *objp, struct array_cache *ac = cpu_cache_get(cachep); check_irq_off(); + if (unlikely(slab_want_init_on_free(cachep))) + memset(objp, 0, cachep->object_size); kmemleak_free_recursive(objp, cachep->flags); objp = cache_free_debugcheck(cachep, objp, caller); @@ -3528,7 +3538,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, cache_alloc_debugcheck_after_bulk(s, flags, size, p, _RET_IP_); /* Clear memory outside IRQ disabled section */ - if (unlikely(flags & __GFP_ZERO)) + if (unlikely(slab_want_init_on_alloc(flags, s))) for (i = 0; i < size; i++) memset(p[i], 0, s->object_size); diff --git a/mm/slab.h b/mm/slab.h index 43ac818b8592..d3f585e604bb 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -524,4 +524,24 @@ static inline int cache_random_seq_create(struct kmem_cache *cachep, static inline void cache_random_seq_destroy(struct kmem_cache *cachep) { } #endif /* CONFIG_SLAB_FREELIST_RANDOM */ +static inline bool slab_want_init_on_alloc(gfp_t flags, struct kmem_cache *c) +{ + if (static_branch_unlikely(&init_on_alloc)) { + if (c->ctor) + return false; + if (c->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) + return flags & __GFP_ZERO; + return true; + } + return flags & __GFP_ZERO; +} + +static inline bool slab_want_init_on_free(struct kmem_cache *c) +{ + if (static_branch_unlikely(&init_on_free)) + return !(c->ctor || + (c->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON))); + return false; +} + #endif /* MM_SLAB_H */ diff --git a/mm/slub.c b/mm/slub.c index cd04dbd2b5d0..3ccdab86f253 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1279,6 +1279,11 @@ static int __init setup_slub_debug(char *str) if (*str == ',') slub_debug_slabs = str + 1; out: + if ((static_branch_unlikely(&init_on_alloc) || + static_branch_unlikely(&init_on_free)) && + (slub_debug & SLAB_POISON)) { + pr_warn("mem auto-init: SLAB_POISON will take precedence over init_on_alloc/init_on_free\n"); + } return 1; } @@ -1424,6 +1429,28 @@ static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x) static inline bool slab_free_freelist_hook(struct kmem_cache *s, void **head, void **tail) { + + void *object; + void *next = *head; + void *old_tail = *tail ? *tail : *head; + int rsize; + + if (slab_want_init_on_free(s)) + do { + object = next; + next = get_freepointer(s, object); + /* + * Clear the object and the metadata, but don't touch + * the redzone. + */ + memset(object, 0, s->object_size); + rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad + : 0; + memset((char *)object + s->inuse, 0, + s->size - s->inuse - rsize); + set_freepointer(s, object, next); + } while (object != old_tail); + /* * Compiler cannot detect this function can be removed if slab_free_hook() * evaluates to nothing. Thus, catch all relevant config debug options here. @@ -1433,9 +1460,7 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s, defined(CONFIG_DEBUG_OBJECTS_FREE) || \ defined(CONFIG_KASAN) - void *object; - void *next = *head; - void *old_tail = *tail ? *tail : *head; + next = *head; /* Head and tail of the reconstructed freelist */ *head = NULL; @@ -2741,8 +2766,14 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, prefetch_freepointer(s, next_object); stat(s, ALLOC_FASTPATH); } + /* + * If the object has been wiped upon free, make sure it's fully + * initialized by zeroing out freelist pointer. + */ + if (unlikely(slab_want_init_on_free(s)) && object) + memset(object + s->offset, 0, sizeof(void *)); - if (unlikely(gfpflags & __GFP_ZERO) && object) + if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object) memset(object, 0, s->object_size); slab_post_alloc_hook(s, gfpflags, 1, &object); @@ -3163,7 +3194,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, local_irq_enable(); /* Clear memory outside IRQ disabled fastpath loop */ - if (unlikely(flags & __GFP_ZERO)) { + if (unlikely(slab_want_init_on_alloc(flags, s))) { int j; for (j = 0; j < i; j++) diff --git a/net/core/sock.c b/net/core/sock.c index af09a23e4822..425e97f693ce 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1596,7 +1596,7 @@ static struct sock *sk_prot_alloc(struct proto *prot, gfp_t priority, sk = kmem_cache_alloc(slab, priority & ~__GFP_ZERO); if (!sk) return sk; - if (priority & __GFP_ZERO) + if (want_init_on_alloc(priority)) sk_prot_clear_nulls(sk, prot->obj_size); } else sk = kmalloc(prot->obj_size, priority); diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index c6cb2d9b2905..a1ffe2eb4d5f 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -160,6 +160,35 @@ config STACKLEAK_RUNTIME_DISABLE runtime to control kernel stack erasing for kernels built with CONFIG_GCC_PLUGIN_STACKLEAK. +config INIT_ON_ALLOC_DEFAULT_ON + bool "Enable heap memory zeroing on allocation by default" + help + This has the effect of setting "init_on_alloc=1" on the kernel + command line. This can be disabled with "init_on_alloc=0". + When "init_on_alloc" is enabled, all page allocator and slab + allocator memory will be zeroed when allocated, eliminating + many kinds of "uninitialized heap memory" flaws, especially + heap content exposures. The performance impact varies by + workload, but most cases see <1% impact. Some synthetic + workloads have measured as high as 7%. + +config INIT_ON_FREE_DEFAULT_ON + bool "Enable heap memory zeroing on free by default" + help + This has the effect of setting "init_on_free=1" on the kernel + command line. This can be disabled with "init_on_free=0". + Similar to "init_on_alloc", when "init_on_free" is enabled, + all page allocator and slab allocator memory will be zeroed + when freed, eliminating many kinds of "uninitialized heap memory" + flaws, especially heap content exposures. The primary difference + with "init_on_free" is that data lifetime in memory is reduced, + as anything freed is wiped immediately, making live forensics or + cold boot memory attacks unable to recover freed memory contents. + The performance impact varies by workload, but is more expensive + than "init_on_alloc" due to the negative cache effects of + touching "cold" memory areas. Most cases see 3-5% impact. Some + synthetic workloads have measured as high as 8%. + endmenu endmenu From patchwork Thu Jun 27 13:03:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Potapenko X-Patchwork-Id: 11019699 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E4F5713B4 for ; Thu, 27 Jun 2019 13:05:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D6BEE28A8E for ; Thu, 27 Jun 2019 13:05:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CA36E28AFD; Thu, 27 Jun 2019 13:05:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 911CD28A8E for ; Thu, 27 Jun 2019 13:05:33 +0000 (UTC) Received: (qmail 29697 invoked by uid 550); 27 Jun 2019 13:05:20 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Delivered-To: moderator for kernel-hardening@lists.openwall.com Received: (qmail 26182 invoked from network); 27 Jun 2019 13:03:43 -0000 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=OTM/dBWKP5pXAZwQDJU1YbjuxxUPU+6Vr1IAcbjuDVo=; b=t+pfh+q2u5DSP6mSeIK1r67ErcoQ4NQ8UsM5O9mGBYMiMCyv5PvcnnHkKNL/S8BSql eOA0/MWF7e5MR4sM/kFj2EDJhvTYzaDf++QwCyebCHUw/KNaIzSHf5WKn4Dt6RpqL+ql DmRJwW/0Je2MaVg41STn0p9q/VP9o0K/qRm0CtcgkzfRUbMccg2EyCxV0U/JM9UsEnlO g62cz0FUurVCddNaeP0ka5lwPT55dY+FEab2GfRuP0XKPq/hulqwOgsctIchPeVNa1M3 ZUJnDFJoRj5ZCGnNG2BOWe67YpXjddedZW0akWlAupL03a82Bk0h6zX7lm6X6NrlCOXf 4+1A== 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=OTM/dBWKP5pXAZwQDJU1YbjuxxUPU+6Vr1IAcbjuDVo=; b=JEMeJyY+ztj50ASmBs5qpwURlNc4vSnJdvNL2P/XgP1SDuUEOaGMIZ3hG2BGgswqG9 spMxpNJyVw7b38V7YoPCcDvSMhwqkCb9VaHV4ehprS7XKBVJS5Ix1Xn2uECXYe37622N aEq1k/bah1lgPJRGlL512RX6/vi2Ucv9v0jG2xpy5FNJG5eRqiqo0KTR3oFELSodeLHq TbUNO2bCINRUhLZxbgePCjsBWMM/8Oal325njoD6Y6JeYCmMo7hd93ITUEP+3qpLo79A SbuVoUtQB5saBCk/HrZf/gnB4+Px4hseOz3ElCLh9uzjZBLmxUn0E3O8T5Bv8VbdOkRL mGbw== X-Gm-Message-State: APjAAAV/xFgI/zmMNtCBF6XZ4wZcXs/jpQPpzDi5BLrITdS1fZC3KRXz giSF+VyrZC94uTGPOqg7O8I0tjkAIWM= X-Google-Smtp-Source: APXvYqzHT3CTIJYzDrs0X3XZhQ1nNpPSVhzaXrDUP0P/c7kcHUZJG8WqtMpRqCMlOADbxQ/YidQWVk8aekg= X-Received: by 2002:a67:bb18:: with SMTP id m24mr1257345vsn.201.1561640612036; Thu, 27 Jun 2019 06:03:32 -0700 (PDT) Date: Thu, 27 Jun 2019 15:03:16 +0200 In-Reply-To: <20190627130316.254309-1-glider@google.com> Message-Id: <20190627130316.254309-3-glider@google.com> Mime-Version: 1.0 References: <20190627130316.254309-1-glider@google.com> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog Subject: [PATCH v9 2/2] mm: init: report memory auto-initialization features at boot time From: Alexander Potapenko To: Andrew Morton , Christoph Lameter Cc: Alexander Potapenko , Kees Cook , Dmitry Vyukov , James Morris , Jann Horn , Kostya Serebryany , Laura Abbott , Mark Rutland , Masahiro Yamada , Matthew Wilcox , Nick Desaulniers , Randy Dunlap , Sandeep Patil , "Serge E. Hallyn" , Souptick Joarder , Marco Elver , Kaiwan N Billimoria , kernel-hardening@lists.openwall.com, linux-mm@kvack.org, linux-security-module@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Print the currently enabled stack and heap initialization modes. Stack initialization is enabled by a config flag, while heap initialization is configured at boot time with defaults being set in the config. It's more convenient for the user to have all information about these hardening measures in one place at boot, so the user can reason about the expected behavior of the running system. The possible options for stack are: - "all" for CONFIG_INIT_STACK_ALL; - "byref_all" for CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL; - "byref" for CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF; - "__user" for CONFIG_GCC_PLUGIN_STRUCTLEAK_USER; - "off" otherwise. Depending on the values of init_on_alloc and init_on_free boottime options we also report "heap alloc" and "heap free" as "on"/"off". In the init_on_free mode initializing pages at boot time may take a while, so print a notice about that as well. This depends on how much memory is installed, the memory bandwidth, etc. On a relatively modern x86 system, it takes about 0.75s/GB to wipe all memory: [ 0.418722] mem auto-init: stack:byref_all, heap alloc:off, heap free:on [ 0.419765] mem auto-init: clearing system memory may take some time... [ 12.376605] Memory: 16408564K/16776672K available (14339K kernel code, 1397K rwdata, 3756K rodata, 1636K init, 11460K bss, 368108K reserved, 0K cma-reserved) Signed-off-by: Alexander Potapenko Suggested-by: Kees Cook Acked-by: Kees Cook To: Andrew Morton To: Christoph Lameter Cc: Dmitry Vyukov Cc: James Morris Cc: Jann Horn Cc: Kostya Serebryany Cc: Laura Abbott Cc: Mark Rutland Cc: Masahiro Yamada Cc: Matthew Wilcox Cc: Nick Desaulniers Cc: Randy Dunlap Cc: Sandeep Patil Cc: "Serge E. Hallyn" Cc: Souptick Joarder Cc: Marco Elver Cc: Kaiwan N Billimoria Cc: kernel-hardening@lists.openwall.com Cc: linux-mm@kvack.org Cc: linux-security-module@vger.kernel.org Signed-off-by: Andrew Morton --- v6: - update patch description, fixed message about clearing memory v7: - rebase the patch, add the Acked-by: tag; - more description updates as suggested by Kees; - make report_meminit() static. v8: - added the Signed-off-by: tag --- init/main.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/init/main.c b/init/main.c index 66a196c5e4c3..ff5803b0841c 100644 --- a/init/main.c +++ b/init/main.c @@ -520,6 +520,29 @@ static inline void initcall_debug_enable(void) } #endif +/* Report memory auto-initialization states for this boot. */ +static void __init report_meminit(void) +{ + const char *stack; + + if (IS_ENABLED(CONFIG_INIT_STACK_ALL)) + stack = "all"; + else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL)) + stack = "byref_all"; + else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)) + stack = "byref"; + else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)) + stack = "__user"; + else + stack = "off"; + + pr_info("mem auto-init: stack:%s, heap alloc:%s, heap free:%s\n", + stack, want_init_on_alloc(GFP_KERNEL) ? "on" : "off", + want_init_on_free() ? "on" : "off"); + if (want_init_on_free()) + pr_info("mem auto-init: clearing system memory may take some time...\n"); +} + /* * Set up kernel memory allocators */ @@ -530,6 +553,7 @@ static void __init mm_init(void) * bigger than MAX_ORDER unless SPARSEMEM. */ page_ext_init_flatmem(); + report_meminit(); mem_init(); kmem_cache_init(); pgtable_init();