From: Jason A. Donenfeld <Jason@zx2c4.com>
Date: Fri, 6 May 2022 14:50:19 +0000 (+0200)
Subject: crypto/rand: fix race on r.used
X-Git-Tag: go1.19beta1~376
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=091e913414794d9176861b1ffcdbcfdc2d742af3;p=gostls13.git

crypto/rand: fix race on r.used

This race is benign, but it still trips up the race detector, so turn
this into an atomic read.

Fixes #52739.

Change-Id: Ib53362286b456513c8c69d6d2d73c6c90ec095f3
Reviewed-on: https://go-review.googlesource.com/c/go/+/404475
Auto-Submit: Jason Donenfeld <Jason@zx2c4.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Jason Donenfeld <Jason@zx2c4.com>
---

diff --git a/src/crypto/rand/rand_unix.go b/src/crypto/rand/rand_unix.go
index 64b865289d..830983c74a 100644
--- a/src/crypto/rand/rand_unix.go
+++ b/src/crypto/rand/rand_unix.go
@@ -59,7 +59,7 @@ func (r *reader) Read(b []byte) (n int, err error) {
 	}
 	if atomic.LoadUint32(&r.used) != 2 {
 		r.mu.Lock()
-		if r.used != 2 {
+		if atomic.LoadUint32(&r.used) != 2 {
 			f, err := os.Open(urandomDevice)
 			if err != nil {
 				r.mu.Unlock()