msan6.go

     1  // Copyright 2018 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 main
     6  
     7  // A C function returning a value on the Go stack could leave the Go
     8  // stack marked as uninitialized, potentially causing a later error
     9  // when the stack is used for something else. Issue 26209.
    10  
    11  /*
    12  #cgo LDFLAGS: -fsanitize=memory
    13  #cgo CPPFLAGS: -fsanitize=memory
    14  
    15  #include <stdint.h>
    16  #include <stdlib.h>
    17  #include <string.h>
    18  
    19  typedef struct {
    20  	uintptr_t a[20];
    21  } S;
    22  
    23  S f() {
    24  	S *p;
    25  
    26  	p = (S *)(malloc(sizeof(S)));
    27  	p->a[0] = 0;
    28  	return *p;
    29  }
    30  */
    31  import "C"
    32  
    33  // allocateStack extends the stack so that stack copying doesn't
    34  // confuse the msan data structures.
    35  //
    36  //go:noinline
    37  func allocateStack(i int) int {
    38  	if i == 0 {
    39  		return i
    40  	}
    41  	return allocateStack(i - 1)
    42  }
    43  
    44  // F1 marks a chunk of stack as uninitialized.
    45  // C.f returns an uninitialized struct on the stack, so msan will mark
    46  // the stack as uninitialized.
    47  //
    48  //go:noinline
    49  func F1() uintptr {
    50  	s := C.f()
    51  	return uintptr(s.a[0])
    52  }
    53  
    54  // F2 allocates a struct on the stack and converts it to an empty interface,
    55  // which will call msanread and see that the data appears uninitialized.
    56  //
    57  //go:noinline
    58  func F2() interface{} {
    59  	return C.S{}
    60  }
    61  
    62  func poisonStack(i int) int {
    63  	if i == 0 {
    64  		return int(F1())
    65  	}
    66  	F1()
    67  	r := poisonStack(i - 1)
    68  	F2()
    69  	return r
    70  }
    71  
    72  func main() {
    73  	allocateStack(16384)
    74  	poisonStack(128)
    75  }
    76
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