From patchwork Thu Jun 9 12:17:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 12875469 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C206BCCA473 for ; Thu, 9 Jun 2022 12:17:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3A7EA8D000A; Thu, 9 Jun 2022 08:17:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 356118D0006; Thu, 9 Jun 2022 08:17:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2202D8D000A; Thu, 9 Jun 2022 08:17:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 1241E8D0006 for ; Thu, 9 Jun 2022 08:17:25 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id D86DD21261 for ; Thu, 9 Jun 2022 12:17:24 +0000 (UTC) X-FDA: 79558597608.07.08CD526 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf04.hostedemail.com (Postfix) with ESMTP id 2A7304006B for ; Thu, 9 Jun 2022 12:17:24 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 3CCC1B82D5C; Thu, 9 Jun 2022 12:17:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 160BCC34114; Thu, 9 Jun 2022 12:17:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1654777038; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=22Iuiuo76qv+0jlpTHCLD62sTQIyeIIPIjWm3iFwPNY=; b=SBU4gzxGLjm86tu6IhpPN6A2mxJHwBPDNxHvfJmB8KR9siYTWTdhgamlGEmURCj5NG0H0M /H/VAeROdJh9/vcJkptTg84PrLi2Ur985cOnyqOZDNwvC3D7jdNYGbUnW/xHMTeOnCpGZK 7V1I+MwcyuC5PR/mmHGP4RJiwX8ORjc= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 1ad02f64 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Thu, 9 Jun 2022 12:17:18 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" , John Ogness , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Geert Uytterhoeven Subject: [PATCH] mm/kfence: select random number before taking raw lock Date: Thu, 9 Jun 2022 14:17:09 +0200 Message-Id: <20220609121709.12939-1-Jason@zx2c4.com> MIME-Version: 1.0 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1654777044; a=rsa-sha256; cv=none; b=8K3/8ivlynozyKLVwu/rtwcasP8EU6Pr3ImzXTpLHeeQC/THgl0yKlPjy+ECMbJ/R3dNsS vZA4y3tvhiG/9SZEseZKfUO/HRIWSDvFGpIDsY09mHOO1vyNjCjhtlqva4a9VxcP5XOA3Y fqz2rErkRDStO5j//xiAyabrEDzf4eg= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1654777044; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references:dkim-signature; bh=22Iuiuo76qv+0jlpTHCLD62sTQIyeIIPIjWm3iFwPNY=; b=ebWl9oJ+44+7/3fuRLaaUVI0ffnuuhq8x6OkYUZ27rRHFSO/ZoT6tIQf3xCDFUL40Rbl5R 4VmEkhgBDSKWZQAsPwn8MMAUJOI5gQGpqZt9b9XE9+fj0jAeNWIfkYJyD/Wj4rhehrkBKZ Pk0up4xYeo67ObHteU7m1iiq6fQMHSM= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=zx2c4.com header.s=20210105 header.b=SBU4gzxG; dmarc=pass (policy=none) header.from=zx2c4.com; spf=pass (imf04.hostedemail.com: domain of "SRS0=TG91=WQ=zx2c4.com=Jason@kernel.org" designates 145.40.68.75 as permitted sender) smtp.mailfrom="SRS0=TG91=WQ=zx2c4.com=Jason@kernel.org" Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=zx2c4.com header.s=20210105 header.b=SBU4gzxG; dmarc=pass (policy=none) header.from=zx2c4.com; spf=pass (imf04.hostedemail.com: domain of "SRS0=TG91=WQ=zx2c4.com=Jason@kernel.org" designates 145.40.68.75 as permitted sender) smtp.mailfrom="SRS0=TG91=WQ=zx2c4.com=Jason@kernel.org" X-Stat-Signature: dropqnu9iaqekysre7un9rmpcxa4wur8 X-Rspamd-Queue-Id: 2A7304006B X-Rspamd-Server: rspam12 X-Rspam-User: X-HE-Tag: 1654777044-172658 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: The RNG uses vanilla spinlocks, not raw spinlocks, so kfence should pick its random numbers before taking its raw spinlocks. This also has the nice effect of doing less work inside the lock. It should fix a splat that Geert saw with CONFIG_PROVE_RAW_LOCK_NESTING: dump_backtrace.part.0+0x98/0xc0 show_stack+0x14/0x28 dump_stack_lvl+0xac/0xec dump_stack+0x14/0x2c __lock_acquire+0x388/0x10a0 lock_acquire+0x190/0x2c0 _raw_spin_lock_irqsave+0x6c/0x94 crng_make_state+0x148/0x1e4 _get_random_bytes.part.0+0x4c/0xe8 get_random_u32+0x4c/0x140 __kfence_alloc+0x460/0x5c4 kmem_cache_alloc_trace+0x194/0x1dc __kthread_create_on_node+0x5c/0x1a8 kthread_create_on_node+0x58/0x7c printk_start_kthread.part.0+0x34/0xa8 printk_activate_kthreads+0x4c/0x54 do_one_initcall+0xec/0x278 kernel_init_freeable+0x11c/0x214 kernel_init+0x24/0x124 ret_from_fork+0x10/0x20 Cc: John Ogness Cc: Alexander Potapenko Cc: Marco Elver Cc: Dmitry Vyukov Reported-by: Geert Uytterhoeven Signed-off-by: Jason A. Donenfeld Tested-by: Geert Uytterhoeven --- mm/kfence/core.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 4e7cd4c8e687..6322b7729b50 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -360,6 +360,9 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g unsigned long flags; struct slab *slab; void *addr; + bool random_right_allocate = prandom_u32_max(2); + bool random_fault = CONFIG_KFENCE_STRESS_TEST_FAULTS && + !prandom_u32_max(CONFIG_KFENCE_STRESS_TEST_FAULTS); /* Try to obtain a free object. */ raw_spin_lock_irqsave(&kfence_freelist_lock, flags); @@ -404,7 +407,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g * is that the out-of-bounds accesses detected are deterministic for * such allocations. */ - if (prandom_u32_max(2)) { + if (random_right_allocate) { /* Allocate on the "right" side, re-calculate address. */ meta->addr += PAGE_SIZE - size; meta->addr = ALIGN_DOWN(meta->addr, cache->align); @@ -444,7 +447,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g if (cache->ctor) cache->ctor(addr); - if (CONFIG_KFENCE_STRESS_TEST_FAULTS && !prandom_u32_max(CONFIG_KFENCE_STRESS_TEST_FAULTS)) + if (random_fault) kfence_protect(meta->addr); /* Random "faults" by protecting the object. */ atomic_long_inc(&counters[KFENCE_COUNTER_ALLOCATED]);