From patchwork Tue Dec 10 12:15:55 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: George Spelvin X-Patchwork-Id: 11463655 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D511E1667 for ; Sat, 28 Mar 2020 16:45:31 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B35EE206F6 for ; Sat, 28 Mar 2020 16:45:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="jzPcj/gf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B35EE206F6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=sdf.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:To:Subject:Date: From:Message-Id:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Owner; bh=OxFlM/dEyO6h8oho0oyL2snATyieOkKTxDThhE1H5+g=; b=jzP cj/gf81Kla1wQjv/WerzYcacbqaD2dGpHk24En0qNN7Qp+/bPWAXZn8MS6vzmBrY4YfkkTNAvQcFz rqRCL2psyrpC3CzFDHE8Q/uI3wTig6kxfkR/vzF3Oad+F65rPvLisjiVw72T5mLYrUZN94G6aqm9N Hys6I6aV4p07XtlCbDTSKRPTs9ZouX6pVhEjbK0wmMXsZY18u44kDlDY/hrnK+ovseJ/iyKv4sSgJ 3sm59Z0J9HsraXyI8qWH5kq2KNNQ5UMweikC03MTKFhrnRMslV8LTy+Yf1l1ZJWYgoKUPzLDu+1JH DfHA/wntg0ry73FajrqvKcI2VqMQlTw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIEaO-00063u-Ur; Sat, 28 Mar 2020 16:45:28 +0000 Received: from mx.sdf.org ([205.166.94.20]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIEaJ-00062d-V8 for linux-arm-kernel@lists.infradead.org; Sat, 28 Mar 2020 16:45:27 +0000 Received: from sdf.org (IDENT:lkml@sdf.lonestar.org [205.166.94.16]) by mx.sdf.org (8.15.2/8.14.5) with ESMTPS id 02SGhObs019651 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits) verified NO); Sat, 28 Mar 2020 16:43:24 GMT Received: (from lkml@localhost) by sdf.org (8.15.2/8.12.8/Submit) id 02SGhOi3016886; Sat, 28 Mar 2020 16:43:24 GMT Message-Id: <202003281643.02SGhOi3016886@sdf.org> From: George Spelvin Date: Tue, 10 Dec 2019 07:15:55 -0500 Subject: [RFC PATCH v1 44/50] arm64: ptr auth: Use get_random_u64 instead of _bytes To: linux-kernel@vger.kernel.org, lkml@sdf.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200328_094526_415969_97B930C6 X-CRM114-Status: GOOD ( 12.29 ) X-Spam-Score: 2.1 (++) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (2.1 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [205.166.94.20 listed in list.dnswl.org] 0.0 SPF_NONE SPF: sender does not publish an SPF Record 2.1 DATE_IN_PAST_96_XX Date: is 96 hours or more before Received: date 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Since these are authentication keys, stored in the kernel as long as they're important, get_random_u64 is fine. In particular, get_random_bytes has significant per-call overhead, so five separate calls is painful. This ended up being a more extensive change, since the previous code was unrolled and 10 calls to get_random_u64() seems excessive. So the code was rearranged to have smaller object size. Currently fields[i] = { 1 << i, 16 * i } for all i could be computed rather than looked up, but the table seemed more future-proof. For ptrauth_keys_switch(), the MSR instructions must be unrolled and are much faster than get_random, so although a similar flags-based interface is possible, it's probably not worth it. Signed-off-by: George Spelvin Cc: Catalin Marinas Cc: Will Deacon Cc: linux-arm-kernel@lists.infradead.org --- arch/arm64/include/asm/pointer_auth.h | 20 +++++---- arch/arm64/kernel/pointer_auth.c | 62 +++++++++++++++------------ 2 files changed, 46 insertions(+), 36 deletions(-) diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h index 7a24bad1a58b8..b7ef71362a3ae 100644 --- a/arch/arm64/include/asm/pointer_auth.h +++ b/arch/arm64/include/asm/pointer_auth.h @@ -30,17 +30,19 @@ struct ptrauth_keys { struct ptrauth_key apga; }; +static inline unsigned long ptrauth_keys_supported(void) +{ + return (system_supports_address_auth() ? + PR_PAC_APIAKEY | PR_PAC_APIBKEY | + PR_PAC_APDAKEY | PR_PAC_APDBKEY : 0) | + (system_supports_generic_auth() ? PR_PAC_APGAKEY : 0); +} + +void ptrauth_keys_generate(struct ptrauth_keys *keys, unsigned long flags); + static inline void ptrauth_keys_init(struct ptrauth_keys *keys) { - if (system_supports_address_auth()) { - get_random_bytes(&keys->apia, sizeof(keys->apia)); - get_random_bytes(&keys->apib, sizeof(keys->apib)); - get_random_bytes(&keys->apda, sizeof(keys->apda)); - get_random_bytes(&keys->apdb, sizeof(keys->apdb)); - } - - if (system_supports_generic_auth()) - get_random_bytes(&keys->apga, sizeof(keys->apga)); + ptrauth_keys_generate(keys, ptrauth_keys_supported()); } #define __ptrauth_key_install(k, v) \ diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c index c507b584259d0..1604ed246128c 100644 --- a/arch/arm64/kernel/pointer_auth.c +++ b/arch/arm64/kernel/pointer_auth.c @@ -7,40 +7,48 @@ #include #include +/* + * Generating crypto-quality random numbers is expensive enough that + * there's no point unrolling this. + */ +void ptrauth_keys_generate(struct ptrauth_keys *keys, unsigned long flags) +{ + size_t i; + static const struct { + /* + * 8 bits is enough for now. Compiler will complain + * if/when we need more. + */ + unsigned char flag, offset; + } fields[] = { + { PR_PAC_APIAKEY, offsetof(struct ptrauth_keys, apia) }, + { PR_PAC_APIBKEY, offsetof(struct ptrauth_keys, apib) }, + { PR_PAC_APDAKEY, offsetof(struct ptrauth_keys, apda) }, + { PR_PAC_APDBKEY, offsetof(struct ptrauth_keys, apdb) }, + { PR_PAC_APGAKEY, offsetof(struct ptrauth_keys, apga) } + }; + + for (i = 0; i < ARRAY_SIZE(fields); i++) { + if (flags & fields[i].flag) { + struct ptrauth_key *k = (void *)keys + fields[i].offset; + k->lo = get_random_u64(); + k->hi = get_random_u64(); + } + } +} + int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg) { + unsigned long supported = ptrauth_keys_supported(); struct ptrauth_keys *keys = &tsk->thread.keys_user; - unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY | - PR_PAC_APDAKEY | PR_PAC_APDBKEY; - unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY; - if (!system_supports_address_auth() && !system_supports_generic_auth()) + if (!supported || arg & ~supported) return -EINVAL; - if (!arg) { - ptrauth_keys_init(keys); - ptrauth_keys_switch(keys); - return 0; - } - - if (arg & ~key_mask) - return -EINVAL; - - if (((arg & addr_key_mask) && !system_supports_address_auth()) || - ((arg & PR_PAC_APGAKEY) && !system_supports_generic_auth())) - return -EINVAL; - - if (arg & PR_PAC_APIAKEY) - get_random_bytes(&keys->apia, sizeof(keys->apia)); - if (arg & PR_PAC_APIBKEY) - get_random_bytes(&keys->apib, sizeof(keys->apib)); - if (arg & PR_PAC_APDAKEY) - get_random_bytes(&keys->apda, sizeof(keys->apda)); - if (arg & PR_PAC_APDBKEY) - get_random_bytes(&keys->apdb, sizeof(keys->apdb)); - if (arg & PR_PAC_APGAKEY) - get_random_bytes(&keys->apga, sizeof(keys->apga)); + if (!arg) + arg = supported; + ptrauth_keys_generate(keys, arg); ptrauth_keys_switch(keys); return 0;