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[209.85.220.73]) by mx.google.com with SMTPS id p186sor2012276oig.128.2019.05.14.07.36.07 for (Google Transport Security); Tue, 14 May 2019 07:36:07 -0700 (PDT) Received-SPF: pass (google.com: domain of 3v9laxaykcfq274z0d2aa270.ya8749gj-886hwy6.ad2@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=HnfouE+v; spf=pass (google.com: domain of 3v9laxaykcfq274z0d2aa270.ya8749gj-886hwy6.ad2@flex--glider.bounces.google.com designates 209.85.220.73 as permitted sender) smtp.mailfrom=3V9LaXAYKCFQ274z0D2AA270.yA8749GJ-886Hwy6.AD2@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=lbdUPdHa+bdM+dxU1m+K2QEpeUH2T4hzEiJEzMD7K4o=; b=HnfouE+vVHCSk/BQWNA2IoM8dz0DlJb1ySFeCJDuDts8JvsGv0c3ABDhxeZs5R1jQ5 fL3ARiq3DAbXqQTqJfJuZH+qPM0Rlxs+eQXmzqAwtxAnJNYEaSrvHiNcxGnelj3HmfgX SSeCx+dAjpm4EnYIiFU/I55GSIaka0an9xHoe2esmSu0PB5SH7by0fAzZu2mm0Mixvs1 WAgEPqulx2gTZH/2wtpBrBL+/yGwJvgPaaOhPEwkgOBXuSvFAk/GEC3w+P2hNj9dN06E 3f5VELZcrJ00AMfyT4YjpAwlQDk+F+t0Pa9AiePOGat0x6TjdKPGnk4TKNYrnaALiQhA jI1g== X-Google-Smtp-Source: APXvYqzwuuntM7HozbX9bxO0OlitRtQOtjK1eJ98Ru/9/M+wLdZyTT23D/aLqfOSqP4W7vywT6UYFvkqKIU= X-Received: by 2002:aca:5f84:: with SMTP id t126mr3137888oib.18.1557844567217; Tue, 14 May 2019 07:36:07 -0700 (PDT) Date: Tue, 14 May 2019 16:35:36 +0200 In-Reply-To: <20190514143537.10435-1-glider@google.com> Message-Id: <20190514143537.10435-4-glider@google.com> Mime-Version: 1.0 References: <20190514143537.10435-1-glider@google.com> X-Mailer: git-send-email 2.21.0.1020.gf2820cf01a-goog Subject: [PATCH v2 3/4] gfp: mm: introduce __GFP_NO_AUTOINIT From: Alexander Potapenko To: akpm@linux-foundation.org, cl@linux.com, keescook@chromium.org Cc: 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 , Souptick Joarder , Matthew Wilcox , linux-mm@kvack.org, linux-security-module@vger.kernel.org Content-Type: text/plain; charset="UTF-8" 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: When passed to an allocator (either pagealloc or SL[AOU]B), __GFP_NO_AUTOINIT tells it to not initialize the requested memory if the init_on_alloc boot option is enabled. This can be useful in the cases newly allocated memory is going to be initialized by the caller right away. __GFP_NO_AUTOINIT doesn't affect init_on_free behavior, except for SLOB, where init_on_free implies init_on_alloc. __GFP_NO_AUTOINIT basically defeats the hardening against information leaks provided by init_on_alloc, so one should use it with caution. This patch also adds __GFP_NO_AUTOINIT to alloc_pages() calls in SL[AOU]B. Doing so is safe, because the heap allocators initialize the pages they receive before passing memory to the callers. Slowdown for the initialization features compared to init_on_free=0, init_on_alloc=0: hackbench, init_on_free=1: +6.84% sys time (st.err 0.74%) hackbench, init_on_alloc=1: +7.25% sys time (st.err 0.72%) Linux build with -j12, init_on_free=1: +8.52% wall time (st.err 0.42%) Linux build with -j12, init_on_free=1: +24.31% sys time (st.err 0.47%) Linux build with -j12, init_on_alloc=1: -0.16% wall time (st.err 0.40%) Linux build with -j12, init_on_alloc=1: +1.24% sys time (st.err 0.39%) The slowdown for init_on_free=0, init_on_alloc=0 compared to the baseline is within the standard error. Signed-off-by: Alexander Potapenko To: Andrew Morton To: Kees Cook To: Christoph Lameter Cc: Masahiro Yamada 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: Souptick Joarder Cc: Matthew Wilcox Cc: linux-mm@kvack.org Cc: linux-security-module@vger.kernel.org Cc: kernel-hardening@lists.openwall.com --- v2: - renamed __GFP_NOINIT to __GFP_NO_AUTOINIT, updated patch name/description --- include/linux/gfp.h | 13 +++++++++---- include/linux/mm.h | 2 +- kernel/kexec_core.c | 3 ++- mm/slab.c | 2 +- mm/slob.c | 3 ++- mm/slub.c | 1 + 6 files changed, 16 insertions(+), 8 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index fdab7de7490d..e1a83bd0ca67 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -44,6 +44,7 @@ struct vm_area_struct; #else #define ___GFP_NOLOCKDEP 0 #endif +#define ___GFP_NO_AUTOINIT 0x1000000u /* If the above are modified, __GFP_BITS_SHIFT may need updating */ /* @@ -208,16 +209,20 @@ struct vm_area_struct; * %__GFP_COMP address compound page metadata. * * %__GFP_ZERO returns a zeroed page on success. + * + * %__GFP_NO_AUTOINIT requests non-initialized memory from the underlying + * allocator. */ -#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_NOWARN ((__force gfp_t)___GFP_NOWARN) +#define __GFP_COMP ((__force gfp_t)___GFP_COMP) +#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) +#define __GFP_NO_AUTOINIT ((__force gfp_t)___GFP_NO_AUTOINIT) /* Disable lockdep for GFP context tracking */ #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) /* Room for N __GFP_FOO bits */ -#define __GFP_BITS_SHIFT (23 + IS_ENABLED(CONFIG_LOCKDEP)) +#define __GFP_BITS_SHIFT (25) #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) /** diff --git a/include/linux/mm.h b/include/linux/mm.h index 18d96f1d07c5..ce6c63396002 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2618,7 +2618,7 @@ DECLARE_STATIC_KEY_FALSE(init_on_alloc); static inline bool want_init_on_alloc(gfp_t flags) { if (static_branch_unlikely(&init_on_alloc)) - return true; + return !(flags & __GFP_NO_AUTOINIT); return flags & __GFP_ZERO; } diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 2f75dd0d0d81..7fc37bacac79 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -302,7 +302,8 @@ static struct page *kimage_alloc_pages(gfp_t gfp_mask, unsigned int order) { struct page *pages; - pages = alloc_pages(gfp_mask & ~__GFP_ZERO, order); + pages = alloc_pages((gfp_mask & ~__GFP_ZERO) | __GFP_NO_AUTOINIT, + order); if (pages) { unsigned int count, i; diff --git a/mm/slab.c b/mm/slab.c index d00e9de26a45..1089461fc22b 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1393,7 +1393,7 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, struct page *page; int nr_pages; - flags |= cachep->allocflags; + flags |= (cachep->allocflags | __GFP_NO_AUTOINIT); page = __alloc_pages_node(nodeid, flags, cachep->gfporder); if (!page) { diff --git a/mm/slob.c b/mm/slob.c index 351d3dfee000..d505f36aa398 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -192,6 +192,7 @@ static void *slob_new_pages(gfp_t gfp, int order, int node) { void *page; + gfp |= __GFP_NO_AUTOINIT; #ifdef CONFIG_NUMA if (node != NUMA_NO_NODE) page = __alloc_pages_node(node, gfp, order); @@ -221,7 +222,7 @@ static inline bool slob_want_init_on_alloc(gfp_t flags, struct kmem_cache *c) { if (static_branch_unlikely(&init_on_alloc) || static_branch_unlikely(&init_on_free)) - return c ? (!c->ctor) : true; + return c ? (!c->ctor) : !(flags & __GFP_NO_AUTOINIT); return flags & __GFP_ZERO; } diff --git a/mm/slub.c b/mm/slub.c index 01424e910800..0aa306f5769a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1495,6 +1495,7 @@ static inline struct page *alloc_slab_page(struct kmem_cache *s, struct page *page; unsigned int order = oo_order(oo); + flags |= __GFP_NO_AUTOINIT; if (node == NUMA_NO_NODE) page = alloc_pages(flags, order); else -- 2.21.0.1020.gf2820cf01a-goog