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[209.85.220.73]) by mx.google.com with SMTPS id g15sor2085907qve.22.2019.04.18.08.42.35 for (Google Transport Security); Thu, 18 Apr 2019 08:42:35 -0700 (PDT) Received-SPF: pass (google.com: domain of 365q4xaykco4wbytuhweewbu.secbydkn-ccalqsa.ehw@flex--glider.bounces.google.com designates 209.85.220.73 as permitted sender) client-ip=209.85.220.73; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=ruHCFZTf; spf=pass (google.com: domain of 365q4xaykco4wbytuhweewbu.secbydkn-ccalqsa.ehw@flex--glider.bounces.google.com designates 209.85.220.73 as permitted sender) smtp.mailfrom=365q4XAYKCO4WbYTUhWeeWbU.SecbYdkn-ccalQSa.ehW@flex--glider.bounces.google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com 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=M9VDOWzYn6nXrWz02ZAfm+oG12axOPQ9eunlREvBT5g=; b=ruHCFZTfTPR7oJ0Q5gBHGMu4QYXz2jROHunlJBX6a9drH/Sem3dfobkW5bOPT8FC91 PbePih1PzsH47kTmoKLiWVDPuTWQ5hxHdYb1v+NA81Jh3zIjR0ryxKrPaxxZxoybQSMF 6evD1/aGfv3F1rkDrjl+6HIJe9mEfvCypDjpC4108XA1+/IP5R8WGDrFhCn7O3PhsMFK emWsI1sxTUKuUZyHA49ncvdSuwwFsxZ+Eq/eu3pqRs1MSYmE6dLTS/LYiTK+Hz/FO+9w WrfOa4C14q1ZratFGNrl8gBCbYzB0EPrGDIuGdvdk5tm6jyJ0BvqzhCy3mS8ifOQeNo3 KvEQ== X-Google-Smtp-Source: APXvYqxCR/g/qmygXOlG5JedEBKs3Cvl/p3zxixLLIJ6SAf3CKB+orRGA7efImjMaMxC2TICPuF3/VUlaYc= X-Received: by 2002:a0c:86cd:: with SMTP id 13mr76282193qvg.146.1555602155603; Thu, 18 Apr 2019 08:42:35 -0700 (PDT) Date: Thu, 18 Apr 2019 17:42:06 +0200 In-Reply-To: <20190418154208.131118-1-glider@google.com> Message-Id: <20190418154208.131118-2-glider@google.com> Mime-Version: 1.0 References: <20190418154208.131118-1-glider@google.com> X-Mailer: git-send-email 2.21.0.392.gf8f6787159e-goog Subject: [PATCH 1/3] mm: security: introduce the init_allocations=1 boot option From: Alexander Potapenko To: akpm@linux-foundation.org, cl@linux.com, dvyukov@google.com, keescook@chromium.org, labbott@redhat.com Cc: linux-mm@kvack.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com 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: X-Virus-Scanned: ClamAV using ClamSMTP This option adds the possibility to initialize newly allocated pages and heap objects with zeroes. This is needed to prevent possible information leaks and make the control-flow bugs that depend on uninitialized values more deterministic. Initialization is done at allocation time at the places where checks for __GFP_ZERO are performed. We don't initialize slab caches with constructors to preserve their semantics. To reduce runtime costs of checking cachep->ctor we replace a call to memset with a call to cachep->poison_fn, which is only executed if the memory block needs to be initialized. For kernel testing purposes filling allocations with a nonzero pattern would be more suitable, but may require platform-specific code. To have a simple baseline we've decided to start with zero-initialization. No performance optimizations are done at the moment to reduce double initialization of memory regions. Signed-off-by: Alexander Potapenko Cc: Andrew Morton Cc: James Morris Cc: "Serge E. Hallyn" Cc: Nick Desaulniers Cc: Kostya Serebryany Cc: Dmitry Vyukov Cc: Kees Cook Cc: Sandeep Patil Cc: Laura Abbott Cc: Randy Dunlap Cc: Jann Horn Cc: Mark Rutland Cc: Qian Cai Cc: Vlastimil Babka Cc: linux-mm@kvack.org Cc: linux-security-module@vger.kernel.org Cc: kernel-hardening@lists.openwall.com --- drivers/infiniband/core/uverbs_ioctl.c | 2 +- include/linux/mm.h | 8 ++++++++ include/linux/slab_def.h | 1 + include/linux/slub_def.h | 1 + kernel/kexec_core.c | 2 +- mm/dmapool.c | 2 +- mm/page_alloc.c | 18 +++++++++++++++++- mm/slab.c | 12 ++++++------ mm/slab.h | 1 + mm/slab_common.c | 15 +++++++++++++++ mm/slob.c | 2 +- mm/slub.c | 8 ++++---- net/core/sock.c | 2 +- 13 files changed, 58 insertions(+), 16 deletions(-) diff --git a/drivers/infiniband/core/uverbs_ioctl.c b/drivers/infiniband/core/uverbs_ioctl.c index e1379949e663..f31234906be2 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_memory(flags)) memset(res, 0, size); return res; } diff --git a/include/linux/mm.h b/include/linux/mm.h index 76769749b5a5..b38b71a5efaa 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2597,6 +2597,14 @@ static inline void kernel_poison_pages(struct page *page, int numpages, int enable) { } #endif +DECLARE_STATIC_KEY_FALSE(init_allocations); +static inline bool want_init_memory(gfp_t flags) +{ + if (static_branch_unlikely(&init_allocations)) + return true; + return flags & __GFP_ZERO; +} + #ifdef CONFIG_DEBUG_PAGEALLOC extern bool _debug_pagealloc_enabled; extern void __kernel_map_pages(struct page *page, int numpages, int enable); diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h index 9a5eafb7145b..9dfe9eb639d7 100644 --- a/include/linux/slab_def.h +++ b/include/linux/slab_def.h @@ -37,6 +37,7 @@ struct kmem_cache { /* constructor func */ void (*ctor)(void *obj); + void (*poison_fn)(struct kmem_cache *c, void *object); /* 4) cache creation/removal */ const char *name; diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index d2153789bd9f..afb928cb7c20 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -99,6 +99,7 @@ struct kmem_cache { gfp_t allocflags; /* gfp flags to use on each alloc */ int refcount; /* Refcount for slab cache destroy */ void (*ctor)(void *); + void (*poison_fn)(struct kmem_cache *c, void *object); unsigned int inuse; /* Offset to metadata */ unsigned int align; /* Alignment */ unsigned int red_left_pad; /* Left redzone padding size */ diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index d7140447be75..be84f5f95c97 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -315,7 +315,7 @@ static struct page *kimage_alloc_pages(gfp_t gfp_mask, unsigned int order) arch_kexec_post_alloc_pages(page_address(pages), count, gfp_mask); - if (gfp_mask & __GFP_ZERO) + if (want_init_memory(gfp_mask)) for (i = 0; i < count; i++) clear_highpage(pages + i); } diff --git a/mm/dmapool.c b/mm/dmapool.c index 76a160083506..796e38160d39 100644 --- a/mm/dmapool.c +++ b/mm/dmapool.c @@ -381,7 +381,7 @@ 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_memory(mem_flags)) memset(retval, 0, pool->size); return retval; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d96ca5bc555b..e2a21d866ac9 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -133,6 +133,22 @@ unsigned long totalcma_pages __read_mostly; int percpu_pagelist_fraction; gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK; +bool want_init_allocations __read_mostly; +EXPORT_SYMBOL(want_init_allocations); +DEFINE_STATIC_KEY_FALSE(init_allocations); + +static int __init early_init_allocations(char *buf) +{ + int ret; + + if (!buf) + return -EINVAL; + ret = kstrtobool(buf, &want_init_allocations); + if (want_init_allocations) + static_branch_enable(&init_allocations); + return ret; +} +early_param("init_allocations", early_init_allocations); /* * A cached value of the page's pageblock's migratetype, used when the page is @@ -2014,7 +2030,7 @@ static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags post_alloc_hook(page, order, gfp_flags); - if (!free_pages_prezeroed() && (gfp_flags & __GFP_ZERO)) + if (!free_pages_prezeroed() && want_init_memory(gfp_flags)) for (i = 0; i < (1 << order); i++) clear_highpage(page + i); diff --git a/mm/slab.c b/mm/slab.c index 47a380a486ee..dcc5b73cf767 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3331,8 +3331,8 @@ 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) - memset(ptr, 0, cachep->object_size); + if (unlikely(want_init_memory(flags)) && ptr) + cachep->poison_fn(cachep, ptr); slab_post_alloc_hook(cachep, flags, 1, &ptr); return ptr; @@ -3388,8 +3388,8 @@ 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) - memset(objp, 0, cachep->object_size); + if (unlikely(want_init_memory(flags)) && objp) + cachep->poison_fn(cachep, objp); slab_post_alloc_hook(cachep, flags, 1, &objp); return objp; @@ -3596,9 +3596,9 @@ 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(want_init_memory(flags))) for (i = 0; i < size; i++) - memset(p[i], 0, s->object_size); + s->poison_fn(s, p[i]); slab_post_alloc_hook(s, flags, size, p); /* FIXME: Trace call missing. Christoph would like a bulk variant */ diff --git a/mm/slab.h b/mm/slab.h index 43ac818b8592..3b541e8970ee 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -27,6 +27,7 @@ struct kmem_cache { const char *name; /* Slab name for sysfs */ int refcount; /* Use counter */ void (*ctor)(void *); /* Called on object slot creation */ + void (*poison_fn)(struct kmem_cache *c, void *object); struct list_head list; /* List of all slab caches on the system */ }; diff --git a/mm/slab_common.c b/mm/slab_common.c index 58251ba63e4a..37810114b2ea 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -360,6 +360,16 @@ struct kmem_cache *find_mergeable(unsigned int size, unsigned int align, return NULL; } +static void poison_zero(struct kmem_cache *c, void *object) +{ + memset(object, 0, c->object_size); +} + +static void poison_dont(struct kmem_cache *c, void *object) +{ + /* Do nothing. Use for caches with constructors. */ +} + static struct kmem_cache *create_cache(const char *name, unsigned int object_size, unsigned int align, slab_flags_t flags, unsigned int useroffset, @@ -381,6 +391,10 @@ static struct kmem_cache *create_cache(const char *name, s->size = s->object_size = object_size; s->align = align; s->ctor = ctor; + if (ctor) + s->poison_fn = poison_dont; + else + s->poison_fn = poison_zero; s->useroffset = useroffset; s->usersize = usersize; @@ -974,6 +988,7 @@ void __init create_boot_cache(struct kmem_cache *s, const char *name, s->align = calculate_alignment(flags, ARCH_KMALLOC_MINALIGN, size); s->useroffset = useroffset; s->usersize = usersize; + s->poison_fn = poison_zero; slab_init_memcg_params(s); diff --git a/mm/slob.c b/mm/slob.c index 307c2c9feb44..18981a71e962 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -330,7 +330,7 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node) BUG_ON(!b); spin_unlock_irqrestore(&slob_lock, flags); } - if (unlikely(gfp & __GFP_ZERO)) + if (unlikely(want_init_memory(gfp))) memset(b, 0, size); return b; } diff --git a/mm/slub.c b/mm/slub.c index d30ede89f4a6..e4efb6575510 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2750,8 +2750,8 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, stat(s, ALLOC_FASTPATH); } - if (unlikely(gfpflags & __GFP_ZERO) && object) - memset(object, 0, s->object_size); + if (unlikely(want_init_memory(gfpflags)) && object) + s->poison_fn(s, object); slab_post_alloc_hook(s, gfpflags, 1, &object); @@ -3172,11 +3172,11 @@ 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(want_init_memory(flags))) { int j; for (j = 0; j < i; j++) - memset(p[j], 0, s->object_size); + s->poison_fn(s, p[j]); } /* memcg and kmem_cache debug support */ diff --git a/net/core/sock.c b/net/core/sock.c index 782343bb925b..99b288a19b39 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1601,7 +1601,7 @@ 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_memory(priority)) sk_prot_clear_nulls(sk, prot->obj_size); } else sk = kmalloc(prot->obj_size, priority);