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1 From e4e59921f1cc11e60f0096bcb4d54dd683270821 Mon Sep 17 00:00:00 2001 |
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2 From: Austin Clements <[email protected]> |
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3 Date: Mon, 24 Aug 2015 13:35:49 -0400 |
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4 Subject: [PATCH 09/63] [release-branch.go1.5] cmd/compile: fix uninitialized |
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5 memory in compare of interface value |
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6 |
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7 A comparison of the form l == r where l is an interface and r is |
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8 concrete performs a type assertion on l to convert it to r's type. |
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9 However, the compiler fails to zero the temporary where the result of |
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10 the type assertion is written, so if the type is a pointer type and a |
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11 stack scan occurs while in the type assertion, it may see an invalid |
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12 pointer on the stack. |
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13 |
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14 Fix this by zeroing the temporary. This is equivalent to the fix for |
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15 type switches from c4092ac. |
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16 |
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17 Fixes #12253. |
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18 |
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19 Change-Id: Iaf205d456b856c056b317b4e888ce892f0c555b9 |
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20 Reviewed-on: https://go-review.googlesource.com/13872 |
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21 Reviewed-by: Russ Cox <[email protected]> |
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22 Reviewed-on: https://go-review.googlesource.com/14242 |
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23 Reviewed-by: Austin Clements <[email protected]> |
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24 --- |
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25 src/cmd/compile/internal/gc/walk.go | 5 +++++ |
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26 src/runtime/export_test.go | 1 + |
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27 src/runtime/gc_test.go | 17 +++++++++++++++++ |
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28 src/runtime/iface.go | 5 +++++ |
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29 4 files changed, 28 insertions(+) |
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30 |
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31 diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go |
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32 index ce73018..af3e1cc 100644 |
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33 --- a/src/cmd/compile/internal/gc/walk.go |
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34 +++ b/src/cmd/compile/internal/gc/walk.go |
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35 @@ -3219,6 +3219,11 @@ func walkcompare(np **Node, init **NodeList) { |
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36 |
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37 if l != nil { |
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38 x := temp(r.Type) |
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39 + if haspointers(r.Type) { |
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40 + a := Nod(OAS, x, nil) |
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41 + typecheck(&a, Etop) |
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42 + *init = list(*init, a) |
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43 + } |
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44 ok := temp(Types[TBOOL]) |
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45 |
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46 // l.(type(r)) |
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47 diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go |
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48 index 16d5476..f14dc30 100644 |
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49 --- a/src/runtime/export_test.go |
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50 +++ b/src/runtime/export_test.go |
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51 @@ -154,3 +154,4 @@ func BenchSetType(n int, x interface{}) { |
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52 const PtrSize = ptrSize |
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53 |
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54 var TestingAssertE2I2GC = &testingAssertE2I2GC |
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55 +var TestingAssertE2T2GC = &testingAssertE2T2GC |
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56 diff --git a/src/runtime/gc_test.go b/src/runtime/gc_test.go |
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57 index 636e524..6c9b314 100644 |
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58 --- a/src/runtime/gc_test.go |
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59 +++ b/src/runtime/gc_test.go |
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60 @@ -469,3 +469,20 @@ func testAssertVar(x interface{}) error { |
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61 } |
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62 return nil |
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63 } |
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64 + |
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65 +func TestAssertE2T2Liveness(t *testing.T) { |
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66 + *runtime.TestingAssertE2T2GC = true |
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67 + defer func() { |
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68 + *runtime.TestingAssertE2T2GC = false |
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69 + }() |
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70 + |
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71 + poisonStack() |
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72 + testIfaceEqual(io.EOF) |
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73 +} |
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74 + |
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75 +func testIfaceEqual(x interface{}) { |
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76 + if x == "abc" { |
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77 + // Prevent inlining |
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78 + panic("") |
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79 + } |
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80 +} |
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81 diff --git a/src/runtime/iface.go b/src/runtime/iface.go |
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82 index abd7068..332b7d5 100644 |
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83 --- a/src/runtime/iface.go |
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84 +++ b/src/runtime/iface.go |
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85 @@ -229,8 +229,13 @@ func assertE2T(t *_type, e interface{}, r unsafe.Pointer) { |
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86 } |
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87 } |
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88 |
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89 +var testingAssertE2T2GC bool |
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90 + |
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91 // The compiler ensures that r is non-nil. |
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92 func assertE2T2(t *_type, e interface{}, r unsafe.Pointer) bool { |
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93 + if testingAssertE2T2GC { |
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94 + GC() |
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95 + } |
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96 ep := (*eface)(unsafe.Pointer(&e)) |
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97 if ep._type != t { |
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98 memclr(r, uintptr(t.size)) |
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99 -- |
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100 2.6.1 |
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101 |