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cmd/compile: detect unsafe conversions from smaller to larger types

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This CL extends the runtime instrumentation for (*T)(ptr) to also
check that the first and last bytes of *(*T)(ptr) are part of the same
heap object.

Updates #22218.
Updates #34959.

Change-Id: I2c8063fe1b7fe6e6145e41c5654cb64dd1c9dd41
Reviewed-on: https://go-review.googlesource.com/c/go/+/201778
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Matthew Dempsky 2019-10-17 12:06:53 -07:00
parent 4edd78d9f8
commit dc72a2f95f
2 changed files with 10 additions and 4 deletions
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2
src/cmd/compile/internal/gc/walk.go
View File

@ -3910,7 +3910,7 @@ func isRuneCount(n *Node) bool {
}
func walkCheckPtrAlignment(n *Node, init *Nodes) *Node {
if n.Type.Elem().Alignment() == 1 {
if n.Type.Elem().Alignment() == 1 && n.Type.Elem().Size() == 1 {
return n
}

12
src/runtime/checkptr.go
View File

@ -7,14 +7,20 @@ package runtime
import "unsafe"
type ptrAlign struct {
ptr unsafe.Pointer
align uintptr
ptr unsafe.Pointer
elem *_type
}
func checkptrAlignment(p unsafe.Pointer, elem *_type) {
// Check that (*T)(p) is appropriately aligned.
// TODO(mdempsky): What about fieldAlign?
if uintptr(p)&(uintptr(elem.align)-1) != 0 {
panic(ptrAlign{p, uintptr(elem.align)})
panic(ptrAlign{p, elem})
}
// Check that (*T)(p) doesn't straddle multiple heap objects.
if elem.size != 1 && checkptrBase(p) != checkptrBase(add(p, elem.size-1)) {
panic(ptrAlign{p, elem})
}
}