From db576c9f3a33d043b4dc6cd8177f4e0b25ded8ec Mon Sep 17 00:00:00 2001 From: Johan Jansson Date: Fri, 1 Apr 2022 14:00:09 +0300 Subject: [PATCH] net/textproto: initialize commonHeader in canonicalMIMEHeaderKey Call initCommonHeader in canonicalMIMEHeaderKey to ensure that commonHeader is initialized before use. Remove all other calls to initCommonHeader, since commonHeader is only used in canonicalMIMEHeaderKey. This prevents a race condition: read of commonHeader before commonHeader has been initialized. Add regression test that triggers the race condition which can be detected by the race detector. Fixes #46363 Change-Id: I00c8c52c6f4c78c0305978c876142c1b388174af Reviewed-on: https://go-review.googlesource.com/c/go/+/397575 Trust: Brad Fitzpatrick Reviewed-by: Bryan Mills Trust: Bryan Mills Run-TryBot: Bryan Mills Auto-Submit: Bryan Mills TryBot-Result: Gopher Robot --- src/net/textproto/reader.go | 4 +--- src/net/textproto/reader_test.go | 29 +++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+), 3 deletions(-) diff --git a/src/net/textproto/reader.go b/src/net/textproto/reader.go index ac47f00700..65974f9cc2 100644 --- a/src/net/textproto/reader.go +++ b/src/net/textproto/reader.go @@ -28,7 +28,6 @@ type Reader struct { // should be reading from an io.LimitReader or similar Reader to bound // the size of responses. func NewReader(r *bufio.Reader) *Reader { - commonHeaderOnce.Do(initCommonHeader) return &Reader{R: r} } @@ -579,8 +578,6 @@ func (r *Reader) upcomingHeaderNewlines() (n int) { // If s contains a space or invalid header field bytes, it is // returned without modifications. func CanonicalMIMEHeaderKey(s string) string { - commonHeaderOnce.Do(initCommonHeader) - // Quick check for canonical encoding. upper := true for i := 0; i < len(s); i++ { @@ -642,6 +639,7 @@ func canonicalMIMEHeaderKey(a []byte) string { a[i] = c upper = c == '-' // for next time } + commonHeaderOnce.Do(initCommonHeader) // The compiler recognizes m[string(byteSlice)] as a special // case, so a copy of a's bytes into a new string does not // happen in this map lookup: diff --git a/src/net/textproto/reader_test.go b/src/net/textproto/reader_test.go index 3124d438fa..d11d40f1cf 100644 --- a/src/net/textproto/reader_test.go +++ b/src/net/textproto/reader_test.go @@ -8,8 +8,10 @@ import ( "bufio" "bytes" "io" + "net" "reflect" "strings" + "sync" "testing" ) @@ -324,6 +326,33 @@ func TestCommonHeaders(t *testing.T) { } } +func TestIssue46363(t *testing.T) { + // Regression test for data race reported in issue 46363: + // ReadMIMEHeader reads commonHeader before commonHeader has been initialized. + // Run this test with the race detector enabled to catch the reported data race. + + // Reset commonHeaderOnce, so that commonHeader will have to be initialized + commonHeaderOnce = sync.Once{} + commonHeader = nil + + // Test for data race by calling ReadMIMEHeader and CanonicalMIMEHeaderKey concurrently + + // Send MIME header over net.Conn + r, w := net.Pipe() + go func() { + // ReadMIMEHeader calls canonicalMIMEHeaderKey, which reads from commonHeader + NewConn(r).ReadMIMEHeader() + }() + w.Write([]byte("A: 1\r\nB: 2\r\nC: 3\r\n\r\n")) + + // CanonicalMIMEHeaderKey calls commonHeaderOnce.Do(initCommonHeader) which initializes commonHeader + CanonicalMIMEHeaderKey("a") + + if commonHeader == nil { + t.Fatal("CanonicalMIMEHeaderKey should initialize commonHeader") + } +} + var clientHeaders = strings.Replace(`Host: golang.org Connection: keep-alive Cache-Control: max-age=0 -- 2.50.0