debug/plan9obj: use saferio to read section data

Avoid allocating large amounts of memory for corrupt input.

No test case because the problem can only happen for invalid data.
Let the fuzzer find cases like this.

Fixes #52521

Change-Id: I6a046f2e28e1255cf773ce135c5bb2b967ef43e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/414234
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dan Kortschak <dan@kortschak.io>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

diff --git a/src/debug/plan9obj/file.go b/src/debug/plan9obj/file.go
index aa0342962422a8500d0248ae68521207385eea38..aa25809148cd40605b754d477269ab7b0b6d79d8 100644 (file)
--- a/src/debug/plan9obj/file.go
+++ b/src/debug/plan9obj/file.go
@@ -9,6 +9,7 @@ import (
        "encoding/binary"
        "errors"
        "fmt"
+       "internal/saferio"
        "io"
        "os"
 )
@@ -55,12 +56,7 @@ type Section struct {
 
 // Data reads and returns the contents of the Plan 9 a.out section.
 func (s *Section) Data() ([]byte, error) {
-       dat := make([]byte, s.sr.Size())
-       n, err := s.sr.ReadAt(dat, 0)
-       if n == len(dat) {
-               err = nil
-       }
-       return dat[0:n], err
+       return saferio.ReadDataAt(s.sr, uint64(s.Size), 0)
 }
 
 // Open returns a new ReadSeeker reading the Plan 9 a.out section.