internal/saferio: new package to avoid OOM

Broken out of debug/pe. Update debug/pe to use it.

For #47653

Change-Id: Ib3037ee04073e005c4b435d0128b8437a075b00a
Reviewed-on: https://go-review.googlesource.com/c/go/+/408678
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dan Kortschak <dan@kortschak.io>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

1 files changed, 2 insertions, 22 deletions

diff --git a/src/debug/pe/string.go b/src/debug/pe/string.go
index 6d9023d8d6..a156bbef05 100644
--- a/src/debug/pe/string.go
+++ b/src/debug/pe/string.go
@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
+	"internal/saferio"
 	"io"
 )
 
@@ -45,28 +46,7 @@ func readStringTable(fh *FileHeader, r io.ReadSeeker) (StringTable, error) {
 	}
 	l -= 4
 
-	// If the string table is large, the file may be corrupt.
-	// Read in chunks to avoid crashing due to out of memory.
-	const chunk = 10 << 20 // 10M
-	var buf []byte
-	if l < chunk {
-		buf = make([]byte, l)
-		_, err = io.ReadFull(r, buf)
-	} else {
-		for l > 0 {
-			n := l
-			if n > chunk {
-				n = chunk
-			}
-			buf1 := make([]byte, n)
-			_, err = io.ReadFull(r, buf1)
-			if err != nil {
-				break
-			}
-			buf = append(buf, buf1...)
-			l -= n
-		}
-	}
+	buf, err := saferio.ReadData(r, uint64(l))
 	if err != nil {
 		return nil, fmt.Errorf("fail to read string table: %v", err)
 	}