From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 66EB8C433FE for ; Thu, 6 Oct 2022 04:54:40 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4MjfHf59Tlz3bvs for ; Thu, 6 Oct 2022 15:54:38 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=chromium.org header.i=@chromium.org header.a=rsa-sha256 header.s=google header.b=FnhfzhzY; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=chromium.org (client-ip=2607:f8b0:4864:20::630; helo=mail-pl1-x630.google.com; envelope-from=keescook@chromium.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=chromium.org header.i=@chromium.org header.a=rsa-sha256 header.s=google header.b=FnhfzhzY; dkim-atps=neutral Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4Mjdwf4Cd4z304J for ; Thu, 6 Oct 2022 15:38:08 +1100 (AEDT) Received: by mail-pl1-x630.google.com with SMTP id u24so636102plq.12 for ; Wed, 05 Oct 2022 21:38:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date; bh=+S5GQGZ6/D/Mg+joUObE0SvwDFyqkvRT2sP5/5vRQvk=; b=FnhfzhzYXlNcl6IxqwADyyzc747mTy8MU4rkgJN+LmLi1BBuM+8meOEr2rKBNA5cdb UV5cg1R4d2Z6xBRg09lXiXAPPCtiRk0FnLoDXMxi1ZwCUSCYDye4OaZgSAusHDiISi0X vF5wP8hNjXz8Z2pcn3GjqjTxVus9QcfOT5k48= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=+S5GQGZ6/D/Mg+joUObE0SvwDFyqkvRT2sP5/5vRQvk=; b=Mm1P77oBKkXLyXFxHPYMv70asrWOrZLI3LrYgZiDD1WrFyLF/rQA2UhC/UZIoMGavx 7hVHaRDdi1CFFTAhU+m8rtpcgU7G3ZxJJ7F0V9jxnQFeu8+0VA5zRV/foKZACxe3mFi2 JTiYIJOgff+xHjEsavvows+PjOhbiZ8a73zQMaUCFU+l+0Kza1cT5w+mvKafFSimZils iDIvZbjzk9WUBcySj7ZiaYYr/UCfJZo2kCDmNPFYkh4JSuTjmmQcCLimU/uiWULnIaEc dEhtiHmpsR2m5Iz766oNwVUsGcjAKWN+dJ9azYrbIISnxyXVBSn5H7GBOHU1ffYiLH0P Y0PQ== X-Gm-Message-State: ACrzQf0XGea5QSOH66kfhcwNnaeBf0EFjE3m4jezxzedF6UvwGfFjf1t kXFLT7BOHXwWvMKmWKYJn+CjhA== X-Google-Smtp-Source: AMsMyM5wQShENjZofrpCE9JXF1y8+Mj33eJ2Bpuqg3wBtAV3umQgBeXMs02cH4EGpzIndWjF3gW38w== X-Received: by 2002:a17:902:db0a:b0:178:2636:b6de with SMTP id m10-20020a170902db0a00b001782636b6demr2822346plx.58.1665031085103; Wed, 05 Oct 2022 21:38:05 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id l18-20020a17090aaa9200b001fd8316db51sm1928521pjq.7.2022.10.05.21.38.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Oct 2022 21:38:03 -0700 (PDT) Date: Wed, 5 Oct 2022 21:38:02 -0700 From: Kees Cook To: "Jason A. Donenfeld" Subject: Re: [PATCH v1 2/5] treewide: use get_random_{u8,u16}() when possible Message-ID: <202210052126.B34A2C62@keescook> References: <20221005214844.2699-1-Jason@zx2c4.com> <20221005214844.2699-3-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221005214844.2699-3-Jason@zx2c4.com> X-Mailman-Approved-At: Thu, 06 Oct 2022 15:52:03 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Lunn , "Darrick J . Wong" , Ulf Hansson , dri-devel@lists.freedesktop.org, Andrii Nakryiko , Hans Verkuil , linux-sctp@vger.kernel.org, "Md . Haris Iqbal" , Miquel Raynal , Christoph Hellwig , Andy Gospodarek , Sergey Matyukevich , Rohit Maheshwari , ceph-devel@vger.kernel.org, Jozsef Kadlecsik , Nilesh Javali , Jean-Paul Roubelat , Dick Kennedy , Jay Vosburgh , Potnuri Bharat Teja , Vinay Kumar Yadav , linux-nfs@vger.kernel.org, Nicholas Piggin , Igor Mitsyanko , Andy Lutomirski , linux-hams@vger.kernel.org, Thomas Gleixner , Trond Myklebust , linux-raid@vger.kernel.org, Neil Horman , Hante Meuleman , Greg Kroah-Hartman , linux-usb@vger.kernel.org, Michael Chan , linux-kernel@vger.kernel.org, Varun Prakash , Chuck Lever , netfilter-devel@vger.kernel.org, Masami Hiramatsu , Jiri Olsa , Jan Kara , linux-fsdevel@vger.kernel.org, Lars Ellenberg , linux-media@vger.kernel.org, Claudiu Beznea , Sharvari Harisangam , linux-fbdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-mmc@vger.kernel.org, Dave Hansen , Song Liu , Eric Dumazet , target-devel@vger.kernel.org, John Stultz , Stanislav Fomichev , Gregory Greenman , drbd-dev@lists.linbit.com, dev@openvswitch.org, Leon Romanovsky , Helge Deller , Hugh Dickins , James Smart , Anil S Keshavamurthy , Pravin B Shelar , Julian Anastasov , coreteam@netfilter.org, Veaceslav Falico , Yonghong Song , Namjae Jeon , linux-crypto@vger.kernel.org, Santosh Shilimkar , Ganapathi Bhat , linux-actions@lists.infradead.org, Simon Horman , Jaegeuk Kim , Mika Westerberg , Andrew Morton , OGAWA Hirofumi , Hao Luo , Theodore Ts'o , Stephen Boyd , Dennis Dalessandro , Florian Westphal , Andreas =?iso-8859-1?Q?F=E4rber?= , Jon Maloy , Vlad Yasevich , Anna Schumaker , Yehezkel Bernat , Haoyue Xu , Heiner Kallweit , linux-wireless@vger.kernel.org, Marcelo Ricardo Leitner , Rasmus Villemoes , linux-nvme@lists.infradead.org, Michal Januszewski , linux-mtd@lists.infradead.org, kasan-dev@googlegroups.com, Cong Wang , Thomas Sailer , Ajay Singh , Xiubo Li , Sagi Grimberg , Daniel Borkmann , Jonathan Corbet , linux-rdma@vger.kernel.org, lvs-devel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "Naveen N . Rao" , Ilya Dryomov , Paolo Abeni , Pablo Neira Ayuso , Marco Elver , Yury Norov , "James E . J . Bottomley" , Jamal Hadi Salim , KP Singh , Borislav Petkov , Keith Busch , Dan Williams , Mauro Carvalho Chehab , Franky Lin , Arend van Spriel , linux-ext4@vger.kernel.org, Wenpeng Liang , "Martin K . Petersen" , Xinming Hu , linux-stm32@st-md-mailman.stormreply.com, Jeff Layton , linux-xfs@vger.kernel.org, netdev@vger.kernel.org, Ying Xue , Manish Rangankar , "David S . Miller" , Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= , Vignesh Raghavendra , Peter Zijlstra , "H . Peter Anvin" , Alexandre Torgue , Amitkumar Karwar , linux-mm@kvack.org, Andreas Dilger , Ayush Sawal , Andreas Noever , Jiri Pirko , linux-f2fs-devel@lists.sourceforge.net, Jack Wang , Steffen Klassert , rds-devel@oss.oracle.com, Herbert Xu , linux-scsi@vger.kernel.org, dccp@vger.kernel.org, Richard Weinberger , Russell King , Jaehoon Chung , Jason Gunthorpe , SHA-cyfmac-dev-list@infineon.com, Ingo Molnar , Jakub Kicinski , John Fastabend , Maxime Coquelin , Manivannan Sadhasivam , Michael Jamet , Kalle Valo , Chao Yu , Akinobu Mita , linux-block@vger.kernel.org, dmaengine@vger.kernel.org, Hannes Reinecke , Andy Shevchenko , Dmitry Vyukov , Jens Axboe , cake@lists.bufferbloat.net, brcm80211-dev-list.pdl@broadcom.com, Yishai Hadas , Hideaki YOSHIFUJI , linuxppc-dev@lists.ozlabs.org, David Ahern , Philipp Reisner , Stephen Hemminger , Christoph =?iso-8859-1?Q?B=F6hmwalder?= , Vinod Koul , tipc-discussion@lists.sourceforge.net, Thomas Graf , Johannes Berg , Sungjong Seo , Martin KaFai Lau Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Oct 05, 2022 at 11:48:41PM +0200, Jason A. Donenfeld wrote: > Rather than truncate a 32-bit value to a 16-bit value or an 8-bit value, > simply use the get_random_{u8,u16}() functions, which are faster than > wasting the additional bytes from a 32-bit value. > > Signed-off-by: Jason A. Donenfeld Same question about "mechanism of transformation". > diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c > index ddfe9208529a..ac452a0111a9 100644 > --- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c > +++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c > @@ -1467,7 +1467,7 @@ static void make_established(struct sock *sk, u32 snd_isn, unsigned int opt) > tp->write_seq = snd_isn; > tp->snd_nxt = snd_isn; > tp->snd_una = snd_isn; > - inet_sk(sk)->inet_id = prandom_u32(); > + inet_sk(sk)->inet_id = get_random_u16(); > assign_rxopt(sk, opt); > > if (tp->rcv_wnd > (RCV_BUFSIZ_M << 10)) This one I had to go look at -- inet_id is u16, so yeah. :) > diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c > index 56ffaa8dd3f6..0131ed2cd1bd 100644 > --- a/lib/test_vmalloc.c > +++ b/lib/test_vmalloc.c > @@ -80,7 +80,7 @@ static int random_size_align_alloc_test(void) > int i; > > for (i = 0; i < test_loop_count; i++) { > - rnd = prandom_u32(); > + rnd = get_random_u8(); > > /* > * Maximum 1024 pages, if PAGE_SIZE is 4096. This wasn't obvious either, but it looks like it's because it never consumes more than u8? > diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c > index 7981be526f26..57c7686ac485 100644 > --- a/net/netfilter/nf_nat_core.c > +++ b/net/netfilter/nf_nat_core.c > @@ -468,7 +468,7 @@ static void nf_nat_l4proto_unique_tuple(struct nf_conntrack_tuple *tuple, > if (range->flags & NF_NAT_RANGE_PROTO_OFFSET) > off = (ntohs(*keyptr) - ntohs(range->base_proto.all)); > else > - off = prandom_u32(); > + off = get_random_u16(); > > attempts = range_size; Yup, u16 off; > diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c > index 2829455211f8..7eb70acb4d58 100644 > --- a/net/sched/sch_sfb.c > +++ b/net/sched/sch_sfb.c > @@ -379,7 +379,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch, > goto enqueue; > } > > - r = prandom_u32() & SFB_MAX_PROB; > + r = get_random_u16() & SFB_MAX_PROB; > > if (unlikely(r < p_min)) { > if (unlikely(p_min > SFB_MAX_PROB / 2)) { include/uapi/linux/pkt_sched.h:#define SFB_MAX_PROB 0xFFFF Reviewed-by: Kees Cook -- Kees Cook