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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id s32sm6108209pgm.19.2019.05.16.17.50.23 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 16 May 2019 17:50:23 -0700 (PDT) Date: Thu, 16 May 2019 17:50:22 -0700 From: Kees Cook To: Alexander Potapenko Cc: akpm@linux-foundation.org, cl@linux.com, kernel-hardening@lists.openwall.com, Masahiro Yamada , James Morris , "Serge E. Hallyn" , Nick Desaulniers , Kostya Serebryany , Dmitry Vyukov , Sandeep Patil , Laura Abbott , Randy Dunlap , Jann Horn , Mark Rutland , linux-mm@kvack.org, linux-security-module@vger.kernel.org Subject: [PATCH 5/4] mm: Introduce SLAB_NO_FREE_INIT and mark excluded caches Message-ID: <201905161746.16E885F@keescook> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190514143537.10435-5-glider@google.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 In order to improve the init_on_free performance, some frequently freed caches with less sensitive contents can be excluded from the init_on_free behavior. This patch is modified from Brad Spengler/PaX Team's code in the last public patch of grsecurity/PaX based on my understanding of the code. Changes or omissions from the original code are mine and don't reflect the original grsecurity/PaX code. Signed-off-by: Kees Cook --- fs/buffer.c | 2 +- fs/dcache.c | 3 ++- include/linux/slab.h | 3 +++ kernel/fork.c | 6 ++++-- mm/rmap.c | 5 +++-- mm/slab.h | 5 +++-- net/core/skbuff.c | 6 ++++-- 7 files changed, 20 insertions(+), 10 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 0faa41fb4c88..04a85bd4cf2e 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -3457,7 +3457,7 @@ void __init buffer_init(void) bh_cachep = kmem_cache_create("buffer_head", sizeof(struct buffer_head), 0, (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| - SLAB_MEM_SPREAD), + SLAB_MEM_SPREAD|SLAB_NO_FREE_INIT), NULL); /* diff --git a/fs/dcache.c b/fs/dcache.c index 8136bda27a1f..323b039accba 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -3139,7 +3139,8 @@ void __init vfs_caches_init_early(void) void __init vfs_caches_init(void) { names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0, - SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL); + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NO_FREE_INIT, 0, + PATH_MAX, NULL); dcache_init(); inode_init(); diff --git a/include/linux/slab.h b/include/linux/slab.h index 9449b19c5f10..7eba9ad8830d 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -92,6 +92,9 @@ /* Avoid kmemleak tracing */ #define SLAB_NOLEAKTRACE ((slab_flags_t __force)0x00800000U) +/* Exclude slab from zero-on-free when init_on_free is enabled */ +#define SLAB_NO_FREE_INIT ((slab_flags_t __force)0x01000000U) + /* Fault injection mark */ #ifdef CONFIG_FAILSLAB # define SLAB_FAILSLAB ((slab_flags_t __force)0x02000000U) diff --git a/kernel/fork.c b/kernel/fork.c index b4cba953040a..9868585f5520 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2550,11 +2550,13 @@ void __init proc_caches_init(void) mm_cachep = kmem_cache_create_usercopy("mm_struct", mm_size, ARCH_MIN_MMSTRUCT_ALIGN, - SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT| + SLAB_NO_FREE_INIT, offsetof(struct mm_struct, saved_auxv), sizeof_field(struct mm_struct, saved_auxv), NULL); - vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); + vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT| + SLAB_NO_FREE_INIT); mmap_init(); nsproxy_cache_init(); } diff --git a/mm/rmap.c b/mm/rmap.c index e5dfe2ae6b0d..b7b8013eeb0a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -432,10 +432,11 @@ static void anon_vma_ctor(void *data) void __init anon_vma_init(void) { anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), - 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT, + 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT| + SLAB_NO_FREE_INIT, anon_vma_ctor); anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, - SLAB_PANIC|SLAB_ACCOUNT); + SLAB_PANIC|SLAB_ACCOUNT|SLAB_NO_FREE_INIT); } /* diff --git a/mm/slab.h b/mm/slab.h index 24ae887359b8..f95b4f03c57b 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -129,7 +129,8 @@ static inline slab_flags_t kmem_cache_flags(unsigned int object_size, /* Legal flag mask for kmem_cache_create(), for various configurations */ #define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | \ SLAB_CACHE_DMA32 | SLAB_PANIC | \ - SLAB_TYPESAFE_BY_RCU | SLAB_DEBUG_OBJECTS ) + SLAB_TYPESAFE_BY_RCU | SLAB_DEBUG_OBJECTS | \ + SLAB_NO_FREE_INIT) #if defined(CONFIG_DEBUG_SLAB) #define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER) @@ -535,7 +536,7 @@ static inline bool slab_want_init_on_alloc(gfp_t flags, struct kmem_cache *c) static inline bool slab_want_init_on_free(struct kmem_cache *c) { if (static_branch_unlikely(&init_on_free)) - return !(c->ctor); + return !(c->ctor) && ((c->flags & SLAB_NO_FREE_INIT) == 0); else return false; } diff --git a/net/core/skbuff.c b/net/core/skbuff.c index e89be6282693..b65902d2c042 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3981,14 +3981,16 @@ void __init skb_init(void) skbuff_head_cache = kmem_cache_create_usercopy("skbuff_head_cache", sizeof(struct sk_buff), 0, - SLAB_HWCACHE_ALIGN|SLAB_PANIC, + SLAB_HWCACHE_ALIGN|SLAB_PANIC| + SLAB_NO_FREE_INIT, offsetof(struct sk_buff, cb), sizeof_field(struct sk_buff, cb), NULL); skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache", sizeof(struct sk_buff_fclones), 0, - SLAB_HWCACHE_ALIGN|SLAB_PANIC, + SLAB_HWCACHE_ALIGN|SLAB_PANIC| + SLAB_NO_FREE_INIT, NULL); skb_extensions_init(); }