From patchwork Tue Jul 12 10:08:29 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Harald Freudenberger X-Patchwork-Id: 12914696 X-Patchwork-Delegate: herbert@gondor.apana.org.au 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 4C777C433EF for ; Tue, 12 Jul 2022 10:08:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232867AbiGLKIs (ORCPT ); Tue, 12 Jul 2022 06:08:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232850AbiGLKIq (ORCPT ); Tue, 12 Jul 2022 06:08:46 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3007D62C1; Tue, 12 Jul 2022 03:08:36 -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 26C9r4Xd000665; Tue, 12 Jul 2022 10:08:35 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=eSHq/Lw6xlRnQULwNWDUKbvDA5yek8lzHeyD2Alq7Os=; b=kNrxpHlKV4m2pzFmEFD8SQDw9/JUx4mwodwnb5DAsLpYbBPZfqtsYPHjVsYrXkxXhxLD CFrh92Vw/PSFOL19Qrl1yYu/7bTM+PhKN9CcuPIZzVWxKXAjjrHTU0zHhypnBwoVRkqk Zen9MDCuYgoYl4oPoHGGjV8hAt9cBCFYq4GDBdEJtcvDq7xhieaRAZbKNhUTuCnGSXkW /NTCfY+Ar8TGWSSdRZLJ1zUX95O3CVF6syoiASpE9C/rAFiiao7NF5sinyXOPAUF0uNy c2nv6zlu8qvUaRlQ14WhidTXsbqVe8mrxnNm+sTDQxLre0GsAjw2pPp87PK5+AYVwXhg rw== Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3h96qf8bc7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 12 Jul 2022 10:08:34 +0000 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 26CA8Qmw010559; Tue, 12 Jul 2022 10:08:33 GMT Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by ppma03ams.nl.ibm.com with ESMTP id 3h71a8v04x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 12 Jul 2022 10:08:33 +0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 26CA8T1724510848 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 12 Jul 2022 10:08:30 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DE4F7AE04D; Tue, 12 Jul 2022 10:08:29 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AB813AE045; Tue, 12 Jul 2022 10:08:29 +0000 (GMT) Received: from funtu.com (unknown [9.145.19.45]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 12 Jul 2022 10:08:29 +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 interrupt context Date: Tue, 12 Jul 2022 12:08:29 +0200 Message-Id: <20220712100829.128574-1-freude@linux.ibm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 6bpfoqfIB9h3LWTuQnWx8WLEUUnpHFpI X-Proofpoint-GUID: 6bpfoqfIB9h3LWTuQnWx8WLEUUnpHFpI 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=2022-07-12_05,2022-07-12_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 bulkscore=0 impostorscore=0 spamscore=0 clxscore=1015 suspectscore=0 mlxscore=0 mlxlogscore=719 phishscore=0 adultscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207120035 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org This patch introduces two things: 1) The arch_get_random_seed_int() implementation now always returns false. There is no user in the whole kernel using this function. 2) For the arch_get_random_seed_long() make sure the CPACF trng instruction is never called in any interrupt context. This is done by adding an additional condition in_task(). Justification for 2): There are some constrains to satisfy for the invocation of the arch_get_random_seed_long() function: - It should provide good random data during kernel initialization. - It should not be called in interrupt context as the 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 | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/arch/s390/include/asm/archrandom.h b/arch/s390/include/asm/archrandom.h index 2c6e1c6ecbe7..9662c9fa7683 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 @@ -33,20 +34,17 @@ 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; } 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; - } return false; }