From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Alexander E. Patrakov" Subject: Re: [PATCH RFC v4 1/1] random: WARN on large getrandom() waits and introduce getrandom2() Date: Sat, 21 Sep 2019 01:11:57 +0500 Message-ID: References: <20190912034421.GA2085@darwi-home-pc> <20190912082530.GA27365@mit.edu> <20190914122500.GA1425@darwi-home-pc> <008f17bc-102b-e762-a17c-e2766d48f515@gmail.com> <20190915052242.GG19710@mit.edu> <20190918211503.GA1808@darwi-home-pc> <20190918211713.GA2225@darwi-home-pc> <20190920134609.GA2113@pc> Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="------------ms020002090106010507010501" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Linus Torvalds , Andy Lutomirski Cc: "Ahmed S. Darwish" , Lennart Poettering , "Theodore Y. Ts'o" , "Eric W. Biederman" , Michael Kerrisk , Willy Tarreau , Matthew Garrett , lkml , Ext4 Developers List , Linux API , linux-man List-Id: linux-api@vger.kernel.org This is a cryptographically signed message in MIME format. --------------ms020002090106010507010501 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-PH Content-Transfer-Encoding: quoted-printable 21.09.2019 00:51, Linus Torvalds =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > And we'll also have to make getrandom(0) be really _timely_. Security > people would likely rather wait for minutes before they are happy with > it. But because it's a boot constraint as things are now, it will not > just be jitter-entropy, it will be _accelerated_ jitter-entropy in 15 > seconds or whatever, and since it can't use up all of CPU time, it's > realistically more like "15 second timeout, but less of actual CPU > time for jitter". I don't think that "accelerated jitter" makes sense. The jitterentropy=20 hwrng that I sent earlier fills the entropy buffer in less than 2=20 seconds, even with quality=3D4, so there is no need to accelerate it even= =20 more. > That said, if we can all convince everybody (hah!) that jitter entropy > in the kernel would be sufficient, then we can make the whole point > entirely moot, and just say "we'll just change crng_wait() to do > jitter entropy instead and be done with it. Then any getrandom() user > will just basically wait for a (very limited) time and the system will > be happy. >=20 > If that is the case we wouldn't need new flags at all. But I don't > think you can make everybody agree to that, which is why I suspect > we'll need the new flag, and I'll just take the heat for saying "0 is > now off limits, because it does this thing that a lot of people > dislike". I 100% agree with that. --=20 Alexander E. 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