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Open Source and information security mailing list archives
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Date: Sat, 8 Oct 2022 22:08:03 +0000 From: David Laight <David.Laight@...LAB.COM> To: "'Jason A. Donenfeld'" <Jason@...c4.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "patches@...ts.linux.dev" <patches@...ts.linux.dev> CC: Andreas Noever <andreas.noever@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Borislav Petkov <bp@...en8.de>, "Catalin Marinas" <catalin.marinas@....com>, Christoph Böhmwalder <christoph.boehmwalder@...bit.com>, Christoph Hellwig <hch@....de>, Christophe Leroy <christophe.leroy@...roup.eu>, Daniel Borkmann <daniel@...earbox.net>, Dave Airlie <airlied@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, "David S . Miller" <davem@...emloft.net>, "Eric Dumazet" <edumazet@...gle.com>, Florian Westphal <fw@...len.de>, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, "H . Peter Anvin" <hpa@...or.com>, Heiko Carstens <hca@...ux.ibm.com>, Helge Deller <deller@....de>, Herbert Xu <herbert@...dor.apana.org.au>, Huacai Chen <chenhuacai@...nel.org>, Hugh Dickins <hughd@...gle.com>, Jakub Kicinski <kuba@...nel.org>, "James E . J . Bottomley" <jejb@...ux.ibm.com>, Jan Kara <jack@...e.com>, Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>, Johannes Berg <johannes@...solutions.net>, Jonathan Corbet <corbet@....net>, Jozsef Kadlecsik <kadlec@...filter.org>, KP Singh <kpsingh@...nel.org>, Kees Cook <keescook@...omium.org>, Marco Elver <elver@...gle.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, "Michael Ellerman" <mpe@...erman.id.au>, Pablo Neira Ayuso <pablo@...filter.org>, "Paolo Abeni" <pabeni@...hat.com>, Peter Zijlstra <peterz@...radead.org>, "Richard Weinberger" <richard@....at>, Russell King <linux@...linux.org.uk>, "Theodore Ts'o" <tytso@....edu>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, "Thomas Gleixner" <tglx@...utronix.de>, Thomas Graf <tgraf@...g.ch>, Ulf Hansson <ulf.hansson@...aro.org>, Vignesh Raghavendra <vigneshr@...com>, WANG Xuerui <kernel@...0n.name>, Will Deacon <will@...nel.org>, Yury Norov <yury.norov@...il.com>, "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>, "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>, "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>, "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>, "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>, "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>, "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>, "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>, "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>, "linux-um@...ts.infradead.org" <linux-um@...ts.infradead.org>, "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>, "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, "loongarch@...ts.linux.dev" <loongarch@...ts.linux.dev>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>, Jan Kara <jack@...e.cz> Subject: RE: [PATCH v4 2/6] treewide: use prandom_u32_max() when possible From: Jason A. Donenfeld > Sent: 07 October 2022 19:01 > > Rather than incurring a division or requesting too many random bytes for > the given range, use the prandom_u32_max() function, which only takes > the minimum required bytes from the RNG and avoids divisions. > ... > --- a/lib/cmdline_kunit.c > +++ b/lib/cmdline_kunit.c > @@ -76,7 +76,7 @@ static void cmdline_test_lead_int(struct kunit *test) > int rc = cmdline_test_values[i]; > int offset; > > - sprintf(in, "%u%s", prandom_u32_max(256), str); > + sprintf(in, "%u%s", get_random_int() % 256, str); > /* Only first '-' after the number will advance the pointer */ > offset = strlen(in) - strlen(str) + !!(rc == 2); > cmdline_do_one_test(test, in, rc, offset); > @@ -94,7 +94,7 @@ static void cmdline_test_tail_int(struct kunit *test) > int rc = strcmp(str, "") ? (strcmp(str, "-") ? 0 : 1) : 1; > int offset; > > - sprintf(in, "%s%u", str, prandom_u32_max(256)); > + sprintf(in, "%s%u", str, get_random_int() % 256); > /* > * Only first and leading '-' not followed by integer > * will advance the pointer. Something has gone backwards here.... And get_random_u8() looks a better fit. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
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