cmd/link/internal/ld: stricter object file decoding

Instead of silently truncating integers to their expected range, check
that they're within range and emit errors if not.  Intended to help
narrow down the cause of issue golang#11617.

Change-Id: Ia7b577270f8438ca7479262702371e26277f1ea7
Reviewed-on: https://go-review.googlesource.com/12050
Reviewed-by: Ian Lance Taylor <[email protected]>

src/cmd/link/internal/ld/objfile.go

@@ -164,22 +164,22 @@ func readsym(ctxt *Link, f *obj.Biobuf, pkg string, pn string) {
 	if obj.Bgetc(f) != 0xfe {
 		log.Fatalf("readsym out of sync")
 	}
-	t := int(rdint(f))
+	t := rdint(f)
 	name := expandpkg(rdstring(f), pkg)
-	v := int(rdint(f))
+	v := rdint(f)
 	if v != 0 && v != 1 {
 		log.Fatalf("invalid symbol version %d", v)
 	}
-	flags := int(rdint(f))
+	flags := rdint(f)
 	dupok := flags & 1
 	local := false
 	if flags&2 != 0 {
 		local = true
 	}
-	size := int(rdint(f))
+	size := rdint(f)
 	typ := rdsym(ctxt, f, pkg)
 	data := rddata(f)
-	nreloc := int(rdint(f))
+	nreloc := rdint(f)
 
 	if v != 0 {
 		v = ctxt.Version
@@ -241,11 +241,11 @@ overwrite:
 		var r *Reloc
 		for i := 0; i < nreloc; i++ {
 			r = &s.R[i]
-			r.Off = int32(rdint(f))
-			r.Siz = uint8(rdint(f))
-			r.Type = int32(rdint(f))
-			r.Add = rdint(f)
-			rdint(f) // Xadd, ignored
+			r.Off = rdint32(f)
+			r.Siz = rduint8(f)
+			r.Type = rdint32(f)
+			r.Add = rdint64(f)
+			rdint64(f) // Xadd, ignored
 			r.Sym = rdsym(ctxt, f, pkg)
 			rdsym(ctxt, f, pkg) // Xsym, ignored
 		}
@@ -260,19 +260,19 @@ overwrite:
 	}
 
 	if s.Type == obj.STEXT {
-		s.Args = int32(rdint(f))
-		s.Locals = int32(rdint(f))
-		s.Nosplit = uint8(rdint(f))
-		v := int(rdint(f))
+		s.Args = rdint32(f)
+		s.Locals = rdint32(f)
+		s.Nosplit = rduint8(f)
+		v := rdint(f)
 		s.Leaf = uint8(v & 1)
 		s.Cfunc = uint8(v & 2)
-		n := int(rdint(f))
+		n := rdint(f)
 		var a *Auto
 		for i := 0; i < n; i++ {
 			a = new(Auto)
 			a.Asym = rdsym(ctxt, f, pkg)
-			a.Aoffset = int32(rdint(f))
-			a.Name = int16(rdint(f))
+			a.Aoffset = rdint32(f)
+			a.Name = rdint16(f)
 			a.Gotype = rdsym(ctxt, f, pkg)
 			a.Link = s.Autom
 			s.Autom = a
@@ -283,23 +283,23 @@ overwrite:
 		pc.Pcsp.P = rddata(f)
 		pc.Pcfile.P = rddata(f)
 		pc.Pcline.P = rddata(f)
-		n = int(rdint(f))
+		n = rdint(f)
 		pc.Pcdata = make([]Pcdata, n)
 		pc.Npcdata = n
 		for i := 0; i < n; i++ {
 			pc.Pcdata[i].P = rddata(f)
 		}
-		n = int(rdint(f))
+		n = rdint(f)
 		pc.Funcdata = make([]*LSym, n)
 		pc.Funcdataoff = make([]int64, n)
 		pc.Nfuncdata = n
 		for i := 0; i < n; i++ {
 			pc.Funcdata[i] = rdsym(ctxt, f, pkg)
 		}
 		for i := 0; i < n; i++ {
-			pc.Funcdataoff[i] = rdint(f)
+			pc.Funcdataoff[i] = rdint64(f)
 		}
-		n = int(rdint(f))
+		n = rdint(f)
 		pc.File = make([]*LSym, n)
 		pc.Nfile = n
 		for i := 0; i < n; i++ {
@@ -374,7 +374,7 @@ overwrite:
 	}
 }
 
-func rdint(f *obj.Biobuf) int64 {
+func rdint64(f *obj.Biobuf) int64 {
 	var c int
 
 	uv := uint64(0)
@@ -392,15 +392,47 @@ func rdint(f *obj.Biobuf) int64 {
 	return int64(uv>>1) ^ (int64(uint64(uv)<<63) >> 63)
 }
 
+func rdint(f *obj.Biobuf) int {
+	n := rdint64(f)
+	if int64(int(n)) != n {
+		log.Panicf("%v out of range for int", n)
+	}
+	return int(n)
+}
+
+func rdint32(f *obj.Biobuf) int32 {
+	n := rdint64(f)
+	if int64(int32(n)) != n {
+		log.Panicf("%v out of range for int32", n)
+	}
+	return int32(n)
+}
+
+func rdint16(f *obj.Biobuf) int16 {
+	n := rdint64(f)
+	if int64(int16(n)) != n {
+		log.Panicf("%v out of range for int16", n)
+	}
+	return int16(n)
+}
+
+func rduint8(f *obj.Biobuf) uint8 {
+	n := rdint64(f)
+	if int64(uint8(n)) != n {
+		log.Panicf("%v out of range for uint8", n)
+	}
+	return uint8(n)
+}
+
 func rdstring(f *obj.Biobuf) string {
-	n := rdint(f)
+	n := rdint64(f)
 	p := make([]byte, n)
 	obj.Bread(f, p)
 	return string(p)
 }
 
 func rddata(f *obj.Biobuf) []byte {
-	n := rdint(f)
+	n := rdint64(f)
 	p := make([]byte, n)
 	obj.Bread(f, p)
 	return p
@@ -409,9 +441,9 @@ func rddata(f *obj.Biobuf) []byte {
 var symbuf []byte
 
 func rdsym(ctxt *Link, f *obj.Biobuf, pkg string) *LSym {
-	n := int(rdint(f))
+	n := rdint(f)
 	if n == 0 {
-		rdint(f)
+		rdint64(f)
 		return nil
 	}
 
@@ -420,7 +452,7 @@ func rdsym(ctxt *Link, f *obj.Biobuf, pkg string) *LSym {
 	}
 	obj.Bread(f, symbuf[:n])
 	p := string(symbuf[:n])
-	v := int(rdint(f))
+	v := rdint(f)
 	if v != 0 {
 		v = ctxt.Version
 	}