From owner-dev-commits-src-main@freebsd.org Tue Jul 20 17:30:34 2021 Return-Path: Delivered-To: dev-commits-src-main@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 05561650421; Tue, 20 Jul 2021 17:30:34 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4GTm2K6VCKz3HjF; Tue, 20 Jul 2021 17:30:33 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id C3E1967CF; Tue, 20 Jul 2021 17:30:33 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 16KHUX6E057551; Tue, 20 Jul 2021 17:30:33 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 16KHUXPM057550; Tue, 20 Jul 2021 17:30:33 GMT (envelope-from git) Date: Tue, 20 Jul 2021 17:30:33 GMT Message-Id: <202107201730.16KHUXPM057550@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Alexander Motin Subject: git: 28d70deaafa6 - main - Fix race between first rand(3) calls. MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: mav X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 28d70deaafa62c5d1602de5272c0aad0fcca8aff Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-main@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for the main branch of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Jul 2021 17:30:34 -0000 The branch main has been updated by mav: URL: https://cgit.FreeBSD.org/src/commit/?id=28d70deaafa62c5d1602de5272c0aad0fcca8aff commit 28d70deaafa62c5d1602de5272c0aad0fcca8aff Author: Alexander Motin AuthorDate: 2021-07-20 17:15:08 +0000 Commit: Alexander Motin CommitDate: 2021-07-20 17:30:28 +0000 Fix race between first rand(3) calls. Before this patch there was a chance for thread that called rand(3) slightly later to see rand3_state already allocated, but not yet initialized. While this API is not expected to be thread-safe, it is not expected to crash. ztest on 64-thread system reproduced it reliably for me. MFC after: 1 month --- lib/libc/stdlib/rand.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/lib/libc/stdlib/rand.c b/lib/libc/stdlib/rand.c index bddb0f040302..353f59349e1d 100644 --- a/lib/libc/stdlib/rand.c +++ b/lib/libc/stdlib/rand.c @@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$"); #include #include #include +#include #include "un-namespace.h" #include "random.h" @@ -68,11 +69,15 @@ static struct __random_state *rand3_state; static void initialize_rand3(void) { + struct __random_state *state; int error; - rand3_state = allocatestate(TYPE_3); - error = initstate_r(rand3_state, 1, rand3_state->rst_randtbl, BREAK_3); + state = allocatestate(TYPE_3); + error = initstate_r(state, 1, state->rst_randtbl, BREAK_3); assert(error == 0); + if (!atomic_cmpset_rel_ptr((volatile uintptr_t *)&rand3_state, + (uintptr_t)NULL, (uintptr_t)state)) + free(state); } int