From patchwork Wed Jul 13 13:17:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Harald Freudenberger X-Patchwork-Id: 590117 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EECABC43334 for ; Wed, 13 Jul 2022 13:19:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236407AbiGMNTf (ORCPT ); Wed, 13 Jul 2022 09:19:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236487AbiGMNTR (ORCPT ); Wed, 13 Jul 2022 09:19:17 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62D9622B2A; Wed, 13 Jul 2022 06:18:51 -0700 (PDT) Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 26DCKTbE007560; Wed, 13 Jul 2022 13:18:40 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding; s=pp1; bh=FUDq9rDjziKvnkVKM0N+vd6elHTrSYRHAeu2ACd6xNA=; b=XPeZXYOM8k+vKeDpFnlYzYLQedGPKR8O8xmAVB0zVBLZeifXmYkZUlrgkDuS3WHterJV ehJs/zQUw0tYy6KppNfZWgV6RsMdifqOqzop+KyYVjRj47buOTtGdDQwA0dcDUpTJEVd Yp1NAEko7OWas+nhS+NkpADX/50m13qdAeAp5Zhvzc8w4gVN8FHLlye22BFWvgKs2qOG YbdmKmK3TZx9JCECf/uYyqPs43CTHQghDgCvShzsu+OYUApexCT5worODH6qZaj4FDNG rdE1RLXLH1a+XJh/eama+Srrq6T1aqh4Lr5yt2DtsmCpAgelHWpT5I3NbKe1iPTWbbVk 5g== Received: from ppma05fra.de.ibm.com (6c.4a.5195.ip4.static.sl-reverse.com [149.81.74.108]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3h9wyjhhkg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 13 Jul 2022 13:18:40 +0000 Received: from pps.filterd (ppma05fra.de.ibm.com [127.0.0.1]) by ppma05fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 26DDBdqa012680; Wed, 13 Jul 2022 13:18:38 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma05fra.de.ibm.com with ESMTP id 3h71a8v9x4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 13 Jul 2022 13:18:38 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 26DDIZpZ16384440 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 13 Jul 2022 13:18:35 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 00AF44C046; Wed, 13 Jul 2022 13:18:35 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B23024C040; Wed, 13 Jul 2022 13:18:34 +0000 (GMT) Received: from funtu.com (unknown [9.145.92.105]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 13 Jul 2022 13:18:34 +0000 (GMT) From: Harald Freudenberger To: linux390-list@tuxmaker.boeblingen.de.ibm.com, linux-crypto@vger.kernel.org, linux-s390@vger.kernel.org, Jason@zx2c4.com Cc: jchrist@linux.ibm.com, dengler@linux.ibm.com Subject: [PATCH] s390/archrandom: remove CPACF trng invocations in irq context Date: Wed, 13 Jul 2022 15:17:21 +0200 Message-Id: <20220713131721.257907-1-freude@linux.ibm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ZJAEM5kf_I633QlJEABShs2uMiIQlmUX X-Proofpoint-ORIG-GUID: ZJAEM5kf_I633QlJEABShs2uMiIQlmUX X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-13_02,2022-07-13_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxlogscore=747 adultscore=0 priorityscore=1501 impostorscore=0 phishscore=0 bulkscore=0 mlxscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207130053 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org This patch slightly reworks the s390 arch_get_random_seed_{int,long} implementation: Make sure the CPACF trng instruction is never called in any interrupt context. This is done by adding an additional condition in_task(). Justification: There are some constrains to satisfy for the invocation of the arch_get_random_seed_{int,long}() functions: - They should provide good random data during kernel initialization. - They should not be called in interrupt context as the TRNG instruction is relatively heavy weight and may for example make some network loads cause to timeout and buck. However, it was not clear what kind of interrupt context is exactly encountered during kernel init or network traffic eventually calling arch_get_random_seed_long(). After some days of investigations it is clear that the s390 start_kernel function is not running in any interrupt context and so the trng is called: Jul 11 18:33:39 t35lp54 kernel: [<00000001064e90ca>] arch_get_random_seed_long.part.0+0x32/0x70 Jul 11 18:33:39 t35lp54 kernel: [<000000010715f246>] random_init+0xf6/0x238 Jul 11 18:33:39 t35lp54 kernel: [<000000010712545c>] start_kernel+0x4a4/0x628 Jul 11 18:33:39 t35lp54 kernel: [<000000010590402a>] startup_continue+0x2a/0x40 The condition in_task() is true and the CPACF trng provides random data during kernel startup. The network traffic however, is more difficult. A typical call stack looks like this: Jul 06 17:37:07 t35lp54 kernel: [<000000008b5600fc>] extract_entropy.constprop.0+0x23c/0x240 Jul 06 17:37:07 t35lp54 kernel: [<000000008b560136>] crng_reseed+0x36/0xd8 Jul 06 17:37:07 t35lp54 kernel: [<000000008b5604b8>] crng_make_state+0x78/0x340 Jul 06 17:37:07 t35lp54 kernel: [<000000008b5607e0>] _get_random_bytes+0x60/0xf8 Jul 06 17:37:07 t35lp54 kernel: [<000000008b56108a>] get_random_u32+0xda/0x248 Jul 06 17:37:07 t35lp54 kernel: [<000000008aefe7a8>] kfence_guarded_alloc+0x48/0x4b8 Jul 06 17:37:07 t35lp54 kernel: [<000000008aeff35e>] __kfence_alloc+0x18e/0x1b8 Jul 06 17:37:07 t35lp54 kernel: [<000000008aef7f10>] __kmalloc_node_track_caller+0x368/0x4d8 Jul 06 17:37:07 t35lp54 kernel: [<000000008b611eac>] kmalloc_reserve+0x44/0xa0 Jul 06 17:37:07 t35lp54 kernel: [<000000008b611f98>] __alloc_skb+0x90/0x178 Jul 06 17:37:07 t35lp54 kernel: [<000000008b6120dc>] __napi_alloc_skb+0x5c/0x118 Jul 06 17:37:07 t35lp54 kernel: [<000000008b8f06b4>] qeth_extract_skb+0x13c/0x680 Jul 06 17:37:07 t35lp54 kernel: [<000000008b8f6526>] qeth_poll+0x256/0x3f8 Jul 06 17:37:07 t35lp54 kernel: [<000000008b63d76e>] __napi_poll.constprop.0+0x46/0x2f8 Jul 06 17:37:07 t35lp54 kernel: [<000000008b63dbec>] net_rx_action+0x1cc/0x408 Jul 06 17:37:07 t35lp54 kernel: [<000000008b937302>] __do_softirq+0x132/0x6b0 Jul 06 17:37:07 t35lp54 kernel: [<000000008abf46ce>] __irq_exit_rcu+0x13e/0x170 Jul 06 17:37:07 t35lp54 kernel: [<000000008abf531a>] irq_exit_rcu+0x22/0x50 Jul 06 17:37:07 t35lp54 kernel: [<000000008b922506>] do_io_irq+0xe6/0x198 Jul 06 17:37:07 t35lp54 kernel: [<000000008b935826>] io_int_handler+0xd6/0x110 Jul 06 17:37:07 t35lp54 kernel: [<000000008b9358a6>] psw_idle_exit+0x0/0xa Jul 06 17:37:07 t35lp54 kernel: ([<000000008ab9c59a>] arch_cpu_idle+0x52/0xe0) Jul 06 17:37:07 t35lp54 kernel: [<000000008b933cfe>] default_idle_call+0x6e/0xd0 Jul 06 17:37:07 t35lp54 kernel: [<000000008ac59f4e>] do_idle+0xf6/0x1b0 Jul 06 17:37:07 t35lp54 kernel: [<000000008ac5a28e>] cpu_startup_entry+0x36/0x40 Jul 06 17:37:07 t35lp54 kernel: [<000000008abb0d90>] smp_start_secondary+0x148/0x158 Jul 06 17:37:07 t35lp54 kernel: [<000000008b935b9e>] restart_int_handler+0x6e/0x90 which confirms that the call is in softirq context. So in_task() covers exactly the cases where we want to have CPACF trng called: not in nmi, not in hard irq, not in soft irq but in normal task context and during kernel init. Signed-off-by: Harald Freudenberger --- arch/s390/include/asm/archrandom.h | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/arch/s390/include/asm/archrandom.h b/arch/s390/include/asm/archrandom.h index 2c6e1c6ecbe7..83ba8aa8b4b0 100644 --- a/arch/s390/include/asm/archrandom.h +++ b/arch/s390/include/asm/archrandom.h @@ -2,7 +2,7 @@ /* * Kernel interface for the s390 arch_random_* functions * - * Copyright IBM Corp. 2017, 2020 + * Copyright IBM Corp. 2017, 2022 * * Author: Harald Freudenberger * @@ -14,6 +14,7 @@ #ifdef CONFIG_ARCH_RANDOM #include +#include #include #include @@ -33,9 +34,11 @@ static inline bool __must_check arch_get_random_int(unsigned int *v) static inline bool __must_check arch_get_random_seed_long(unsigned long *v) { if (static_branch_likely(&s390_arch_random_available)) { - cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v)); - atomic64_add(sizeof(*v), &s390_arch_random_counter); - return true; + if (in_task()) { + cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v)); + atomic64_add(sizeof(*v), &s390_arch_random_counter); + return true; + } } return false; } @@ -43,9 +46,11 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v) static inline bool __must_check arch_get_random_seed_int(unsigned int *v) { if (static_branch_likely(&s390_arch_random_available)) { - cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v)); - atomic64_add(sizeof(*v), &s390_arch_random_counter); - return true; + if (in_task()) { + cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v)); + atomic64_add(sizeof(*v), &s390_arch_random_counter); + return true; + } } return false; }