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Open Source and information security mailing list archives
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Date: Thu, 6 Oct 2022 16:20:31 +0300 From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com> To: "Jason A. Donenfeld" <Jason@...c4.com> Cc: Jason Gunthorpe <jgg@...pe.ca>, linux-kernel@...r.kernel.org, brcm80211-dev-list.pdl@...adcom.com, cake@...ts.bufferbloat.net, ceph-devel@...r.kernel.org, coreteam@...filter.org, dccp@...r.kernel.org, dev@...nvswitch.org, dmaengine@...r.kernel.org, drbd-dev@...ts.linbit.com, dri-devel@...ts.freedesktop.org, kasan-dev@...glegroups.com, linux-actions@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, linux-block@...r.kernel.org, linux-crypto@...r.kernel.org, linux-doc@...r.kernel.org, linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, linux-fbdev@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-hams@...r.kernel.org, linux-media@...r.kernel.org, linux-mm@...ck.org, linux-mmc@...r.kernel.org, linux-mtd@...ts.infradead.org, linux-nfs@...r.kernel.org, linux-nvme@...ts.infradead.org, linux-raid@...r.kernel.org, linux-rdma@...r.kernel.org, linux-scsi@...r.kernel.org, linux-sctp@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com, linux-usb@...r.kernel.org, linux-wireless@...r.kernel.org, linux-xfs@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, lvs-devel@...r.kernel.org, netdev@...r.kernel.org, netfilter-devel@...r.kernel.org, rds-devel@....oracle.com, SHA-cyfmac-dev-list@...ineon.com, target-devel@...r.kernel.org, tipc-discussion@...ts.sourceforge.net Subject: Re: [PATCH v1 3/5] treewide: use get_random_u32() when possible On Thu, Oct 06, 2022 at 07:05:48AM -0600, Jason A. Donenfeld wrote: > On Thu, Oct 6, 2022 at 6:47 AM Jason Gunthorpe <jgg@...pe.ca> wrote: > > On Wed, Oct 05, 2022 at 11:48:42PM +0200, Jason A. Donenfeld wrote: ... > > > - u32 isn = (prandom_u32() & ~7UL) - 1; > > > + u32 isn = (get_random_u32() & ~7UL) - 1; > > > > Maybe this wants to be written as > > > > (prandom_max(U32_MAX >> 7) << 7) | 7 > > ? > > Holy smokes. Yea I guess maybe? It doesn't exactly gain anything or > make the code clearer though, and is a little bit more magical than > I'd like on a first pass. Shouldn't the two first 7s to be 3s? ... > > > - psn = prandom_u32() & 0xffffff; > > > + psn = get_random_u32() & 0xffffff; > > > > prandom_max(0xffffff + 1) > > That'd work, but again it's not more clear. Authors here are going for > a 24-bit number, and masking seems like a clear way to express that. We have some 24-bit APIs (and 48-bit) already in kernel, why not to have get_random_u24() ? -- With Best Regards, Andy Shevchenko
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