| 1 | // Copyright 2020 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // Package sigchanyzer defines an Analyzer that detects |
| 6 | // misuse of unbuffered signal as argument to signal.Notify. |
| 7 | package sigchanyzer |
| 8 | |
| 9 | import ( |
| 10 | "bytes" |
| 11 | "go/ast" |
| 12 | "go/format" |
| 13 | "go/token" |
| 14 | "go/types" |
| 15 | |
| 16 | "golang.org/x/tools/go/analysis" |
| 17 | "golang.org/x/tools/go/analysis/passes/inspect" |
| 18 | "golang.org/x/tools/go/ast/inspector" |
| 19 | ) |
| 20 | |
| 21 | const Doc = `check for unbuffered channel of os.Signal |
| 22 | |
| 23 | This checker reports call expression of the form signal.Notify(c <-chan os.Signal, sig ...os.Signal), |
| 24 | where c is an unbuffered channel, which can be at risk of missing the signal.` |
| 25 | |
| 26 | // Analyzer describes sigchanyzer analysis function detector. |
| 27 | var Analyzer = &analysis.Analyzer{ |
| 28 | Name: "sigchanyzer", |
| 29 | Doc: Doc, |
| 30 | Requires: []*analysis.Analyzer{inspect.Analyzer}, |
| 31 | Run: run, |
| 32 | } |
| 33 | |
| 34 | func run(pass *analysis.Pass) (interface{}, error) { |
| 35 | inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector) |
| 36 | |
| 37 | nodeFilter := []ast.Node{ |
| 38 | (*ast.CallExpr)(nil), |
| 39 | } |
| 40 | inspect.Preorder(nodeFilter, func(n ast.Node) { |
| 41 | call := n.(*ast.CallExpr) |
| 42 | if !isSignalNotify(pass.TypesInfo, call) { |
| 43 | return |
| 44 | } |
| 45 | var chanDecl *ast.CallExpr |
| 46 | switch arg := call.Args[0].(type) { |
| 47 | case *ast.Ident: |
| 48 | if decl, ok := findDecl(arg).(*ast.CallExpr); ok { |
| 49 | chanDecl = decl |
| 50 | } |
| 51 | case *ast.CallExpr: |
| 52 | // Only signal.Notify(make(chan os.Signal), os.Interrupt) is safe, |
| 53 | // conservatively treat others as not safe, see golang/go#45043 |
| 54 | if isBuiltinMake(pass.TypesInfo, arg) { |
| 55 | return |
| 56 | } |
| 57 | chanDecl = arg |
| 58 | } |
| 59 | if chanDecl == nil || len(chanDecl.Args) != 1 { |
| 60 | return |
| 61 | } |
| 62 | |
| 63 | // Make a copy of the channel's declaration to avoid |
| 64 | // mutating the AST. See https://golang.org/issue/46129. |
| 65 | chanDeclCopy := &ast.CallExpr{} |
| 66 | *chanDeclCopy = *chanDecl |
| 67 | chanDeclCopy.Args = append([]ast.Expr(nil), chanDecl.Args...) |
| 68 | chanDeclCopy.Args = append(chanDeclCopy.Args, &ast.BasicLit{ |
| 69 | Kind: token.INT, |
| 70 | Value: "1", |
| 71 | }) |
| 72 | |
| 73 | var buf bytes.Buffer |
| 74 | if err := format.Node(&buf, token.NewFileSet(), chanDeclCopy); err != nil { |
| 75 | return |
| 76 | } |
| 77 | pass.Report(analysis.Diagnostic{ |
| 78 | Pos: call.Pos(), |
| 79 | End: call.End(), |
| 80 | Message: "misuse of unbuffered os.Signal channel as argument to signal.Notify", |
| 81 | SuggestedFixes: []analysis.SuggestedFix{{ |
| 82 | Message: "Change to buffer channel", |
| 83 | TextEdits: []analysis.TextEdit{{ |
| 84 | Pos: chanDecl.Pos(), |
| 85 | End: chanDecl.End(), |
| 86 | NewText: buf.Bytes(), |
| 87 | }}, |
| 88 | }}, |
| 89 | }) |
| 90 | }) |
| 91 | return nil, nil |
| 92 | } |
| 93 | |
| 94 | func isSignalNotify(info *types.Info, call *ast.CallExpr) bool { |
| 95 | check := func(id *ast.Ident) bool { |
| 96 | obj := info.ObjectOf(id) |
| 97 | return obj.Name() == "Notify" && obj.Pkg().Path() == "os/signal" |
| 98 | } |
| 99 | switch fun := call.Fun.(type) { |
| 100 | case *ast.SelectorExpr: |
| 101 | return check(fun.Sel) |
| 102 | case *ast.Ident: |
| 103 | if fun, ok := findDecl(fun).(*ast.SelectorExpr); ok { |
| 104 | return check(fun.Sel) |
| 105 | } |
| 106 | return false |
| 107 | default: |
| 108 | return false |
| 109 | } |
| 110 | } |
| 111 | |
| 112 | func findDecl(arg *ast.Ident) ast.Node { |
| 113 | if arg.Obj == nil { |
| 114 | return nil |
| 115 | } |
| 116 | switch as := arg.Obj.Decl.(type) { |
| 117 | case *ast.AssignStmt: |
| 118 | if len(as.Lhs) != len(as.Rhs) { |
| 119 | return nil |
| 120 | } |
| 121 | for i, lhs := range as.Lhs { |
| 122 | lid, ok := lhs.(*ast.Ident) |
| 123 | if !ok { |
| 124 | continue |
| 125 | } |
| 126 | if lid.Obj == arg.Obj { |
| 127 | return as.Rhs[i] |
| 128 | } |
| 129 | } |
| 130 | case *ast.ValueSpec: |
| 131 | if len(as.Names) != len(as.Values) { |
| 132 | return nil |
| 133 | } |
| 134 | for i, name := range as.Names { |
| 135 | if name.Obj == arg.Obj { |
| 136 | return as.Values[i] |
| 137 | } |
| 138 | } |
| 139 | } |
| 140 | return nil |
| 141 | } |
| 142 | |
| 143 | func isBuiltinMake(info *types.Info, call *ast.CallExpr) bool { |
| 144 | typVal := info.Types[call.Fun] |
| 145 | if !typVal.IsBuiltin() { |
| 146 | return false |
| 147 | } |
| 148 | switch fun := call.Fun.(type) { |
| 149 | case *ast.Ident: |
| 150 | return info.ObjectOf(fun).Name() == "make" |
| 151 | default: |
| 152 | return false |
| 153 | } |
| 154 | } |
| 155 |
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