mirror of
https://github.com/golang/go
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71 lines
4.1 KiB
Go
71 lines
4.1 KiB
Go
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// run
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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This test is not for a fix of 29312 proper, but for the patch that
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// makes sure we at least don't have a security hole because of 29312.
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// This code generates lots of types. The binary should contain
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// a runtime.slicetype for each of the following 253 types:
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//
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// []*pwn
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// [][]*pwn
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// ...
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// [][]...[][]*pwn - 249 total "[]"
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// [][]...[][][]*pwn - 250 total "[]"
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// [][]...[][][][]*pwn - 251 total "[]"
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// [][]...[][][][][]*pwn - 252 total "[]"
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// [][]...[][][][][][]*pwn - 253 total "[]"
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//
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// The type names for these types are as follows. Because we truncate
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// the name at depth 250, the last few names are all identical:
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//
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// type.[]*"".pwn
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// type.[][]*"".pwn
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// ...
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// type.[][]...[][]*pwn - 249 total "[]"
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// type.[][]...[][][]*<...> - 250 total "[]"
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// type.[][]...[][][][]<...> - 251 total "[]"
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// type.[][]...[][][][]<...> - 252 total "[]" (but only 251 "[]" in the name)
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// type.[][]...[][][][]<...> - 253 total "[]" (but only 251 "[]" in the name)
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//
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// Because the names of the last 3 types are all identical, the
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// compiler will generate only a single runtime.slicetype data
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// structure for all 3 underlying types. It turns out the compiler
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// generates just the 251-entry one. There aren't any
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// runtime.slicetypes generated for the final two types.
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//
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// The compiler passes type.[]...[]<...> (251 total "[]") to
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// fmt.Sprintf (instead of the correct 253 one). But the data
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// structure at runtime actually has 253 nesting levels. So we end up
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// calling String on something that is of type [][]*pwn instead of
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// something of type *pwn. The way arg passing in Go works, the
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// backing store pointer for the outer slice becomes the "this"
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// pointer of the String method, which points to the inner []*pwn
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// slice. The String method then modifies the length of that inner
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// slice.
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package main
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import "fmt"
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type pwn struct {
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a [3]uint
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}
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func (this *pwn) String() string {
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this.a[1] = 7 // update length
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return ""
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}
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func main() {
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var a pwn
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s := [][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]*pwn{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{&a}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}} // depth 253
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fmt.Sprint(s)
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n := len(s[0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0]) // depth 252, type []*pwn
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if n != 1 {
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panic(fmt.Sprintf("length was changed, want 1 got %d", n))
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}
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}
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