From 61bc17f04e232a62204b78b68e839db7029338d7 Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Tue, 28 Mar 2023 10:19:21 -0700 Subject: [PATCH] cmd/compile: don't assume pointer of a slice is non-nil unsafe.SliceData can return pointers which are nil. That function gets lowered to the SSA OpSlicePtr, which the compiler assumes is non-nil. This used to be the case as OpSlicePtr was only used in situations where the bounds check already passed. But with unsafe.SliceData that is no longer the case. There are situations where we know it is nil. Use Bounded() to indicate that. I looked through all the uses of OSPTR and added SetBounded where it made sense. Most OSPTR results are passed directly to runtime calls (e.g. memmove), so even if we know they are non-nil that info isn't helpful. Fixes #59293 Change-Id: I437a15330db48e0082acfb1f89caf8c56723fc51 Reviewed-on: https://go-review.googlesource.com/c/go/+/479896 Reviewed-by: Matthew Dempsky Reviewed-by: Keith Randall TryBot-Result: Gopher Robot Run-TryBot: Keith Randall --- src/cmd/compile/internal/ir/node.go | 2 +- src/cmd/compile/internal/ssagen/ssa.go | 5 ++++- src/cmd/compile/internal/walk/convert.go | 4 +++- src/cmd/compile/internal/walk/range.go | 1 + test/fixedbugs/issue59293.go | 28 ++++++++++++++++++++++++ 5 files changed, 37 insertions(+), 3 deletions(-) create mode 100644 test/fixedbugs/issue59293.go diff --git a/src/cmd/compile/internal/ir/node.go b/src/cmd/compile/internal/ir/node.go index ad25b9ff32..bdc40a8e7c 100644 --- a/src/cmd/compile/internal/ir/node.go +++ b/src/cmd/compile/internal/ir/node.go @@ -292,7 +292,7 @@ const ( OEFACE // itable and data words of an empty-interface value. OITAB // itable word of an interface value. OIDATA // data word of an interface value in X - OSPTR // base pointer of a slice or string. + OSPTR // base pointer of a slice or string. Bounded==1 means known non-nil. OCFUNC // reference to c function pointer (not go func value) OCHECKNIL // emit code to ensure pointer/interface not nil ORESULT // result of a function call; Xoffset is stack offset diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go index e49ba5ee71..a37604963f 100644 --- a/src/cmd/compile/internal/ssagen/ssa.go +++ b/src/cmd/compile/internal/ssagen/ssa.go @@ -3199,7 +3199,10 @@ func (s *state) exprCheckPtr(n ir.Node, checkPtrOK bool) *ssa.Value { n := n.(*ir.UnaryExpr) a := s.expr(n.X) if n.X.Type().IsSlice() { - return s.newValue1(ssa.OpSlicePtr, n.Type(), a) + if n.Bounded() { + return s.newValue1(ssa.OpSlicePtr, n.Type(), a) + } + return s.newValue1(ssa.OpSlicePtrUnchecked, n.Type(), a) } else { return s.newValue1(ssa.OpStringPtr, n.Type(), a) } diff --git a/src/cmd/compile/internal/walk/convert.go b/src/cmd/compile/internal/walk/convert.go index 07ddd0458f..bfa0c5480f 100644 --- a/src/cmd/compile/internal/walk/convert.go +++ b/src/cmd/compile/internal/walk/convert.go @@ -281,7 +281,9 @@ func walkStringToBytes(n *ir.ConvExpr, init *ir.Nodes) ir.Node { // Copy from the static string data to the [n]byte. if len(sc) > 0 { - as := ir.NewAssignStmt(base.Pos, ir.NewStarExpr(base.Pos, p), ir.NewStarExpr(base.Pos, typecheck.ConvNop(ir.NewUnaryExpr(base.Pos, ir.OSPTR, s), t.PtrTo()))) + sptr := ir.NewUnaryExpr(base.Pos, ir.OSPTR, s) + sptr.SetBounded(true) + as := ir.NewAssignStmt(base.Pos, ir.NewStarExpr(base.Pos, p), ir.NewStarExpr(base.Pos, typecheck.ConvNop(sptr, t.PtrTo()))) appendWalkStmt(init, as) } diff --git a/src/cmd/compile/internal/walk/range.go b/src/cmd/compile/internal/walk/range.go index e20ffc2a61..1d757a62a5 100644 --- a/src/cmd/compile/internal/walk/range.go +++ b/src/cmd/compile/internal/walk/range.go @@ -193,6 +193,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node { // Pointer to current iteration position. Start on entry to the loop // with the pointer in hu. ptr := ir.NewUnaryExpr(base.Pos, ir.OSPTR, hs) + ptr.SetBounded(true) huVal := ir.NewConvExpr(base.Pos, ir.OCONVNOP, types.Types[types.TUNSAFEPTR], ptr) huVal = ir.NewConvExpr(base.Pos, ir.OCONVNOP, types.Types[types.TUINTPTR], huVal) hu := typecheck.Temp(types.Types[types.TUINTPTR]) diff --git a/test/fixedbugs/issue59293.go b/test/fixedbugs/issue59293.go new file mode 100644 index 0000000000..1f05fe9a7a --- /dev/null +++ b/test/fixedbugs/issue59293.go @@ -0,0 +1,28 @@ +// run + +// Copyright 2023 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package main + +import "unsafe" + +//go:noinline +func f(x []byte) bool { + return unsafe.SliceData(x) != nil +} + +//go:noinline +func g(x string) bool { + return unsafe.StringData(x) != nil +} + +func main() { + if f(nil) { + panic("bad f") + } + if g("") { + panic("bad g") + } +}