debug/buildinfo: use saferio in ReadData methods

This avoids a very large memory allocation if corrupt data says that
we need to read a very long string.

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

For #47653
Fixes #58886

Change-Id: I4e80ba62a6416d010c8804e4f49ae81bdafaadb8
Reviewed-on: https://go-review.googlesource.com/c/go/+/473657
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/debug/buildinfo/buildinfo.go b/src/debug/buildinfo/buildinfo.go
index 8bc5753a2d71ce31e71b8856037d8e32dceb2ece..a7019a666e2aa4d12491ac936a99efb4c20ec3eb 100644 (file)
--- a/src/debug/buildinfo/buildinfo.go
+++ b/src/debug/buildinfo/buildinfo.go
@@ -19,6 +19,7 @@ import (
        "encoding/binary"
        "errors"
        "fmt"
+       "internal/saferio"
        "internal/xcoff"
        "io"
        "io/fs"
@@ -260,12 +261,7 @@ func (x *elfExe) ReadData(addr, size uint64) ([]byte, error) {
                        if n > size {
                                n = size
                        }
-                       data := make([]byte, n)
-                       _, err := prog.ReadAt(data, int64(addr-prog.Vaddr))
-                       if err != nil {
-                               return nil, err
-                       }
-                       return data, nil
+                       return saferio.ReadDataAt(prog, n, int64(addr-prog.Vaddr))
                }
        }
        return nil, errUnrecognizedFormat
@@ -308,12 +304,7 @@ func (x *peExe) ReadData(addr, size uint64) ([]byte, error) {
                        if n > size {
                                n = size
                        }
-                       data := make([]byte, n)
-                       _, err := sect.ReadAt(data, int64(addr-uint64(sect.VirtualAddress)))
-                       if err != nil {
-                               return nil, errUnrecognizedFormat
-                       }
-                       return data, nil
+                       return saferio.ReadDataAt(sect, n, int64(addr-uint64(sect.VirtualAddress)))
                }
        }
        return nil, errUnrecognizedFormat
@@ -360,12 +351,7 @@ func (x *machoExe) ReadData(addr, size uint64) ([]byte, error) {
                        if n > size {
                                n = size
                        }
-                       data := make([]byte, n)
-                       _, err := seg.ReadAt(data, int64(addr-seg.Addr))
-                       if err != nil {
-                               return nil, err
-                       }
-                       return data, nil
+                       return saferio.ReadDataAt(seg, n, int64(addr-seg.Addr))
                }
        }
        return nil, errUnrecognizedFormat
@@ -401,12 +387,7 @@ func (x *xcoffExe) ReadData(addr, size uint64) ([]byte, error) {
                        if n > size {
                                n = size
                        }
-                       data := make([]byte, n)
-                       _, err := sect.ReadAt(data, int64(addr-sect.VirtualAddress))
-                       if err != nil {
-                               return nil, err
-                       }
-                       return data, nil
+                       return saferio.ReadDataAt(sect, n, int64(addr-sect.VirtualAddress))
                }
        }
        return nil, errors.New("address not mapped")
@@ -438,12 +419,7 @@ func (x *plan9objExe) ReadData(addr, size uint64) ([]byte, error) {
                        if n > size {
                                n = size
                        }
-                       data := make([]byte, n)
-                       _, err := sect.ReadAt(data, int64(addr-uint64(sect.Offset)))
-                       if err != nil {
-                               return nil, err
-                       }
-                       return data, nil
+                       return saferio.ReadDataAt(sect, n, int64(addr-uint64(sect.Offset)))
                }
        }
        return nil, errors.New("address not mapped")