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fix unsafe .ptr accesses in druntime #1590

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yebblies merged 1 commit into from
Jun 13, 2016
Merged

fix unsafe .ptr accesses in druntime #1590

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4 changes: 2 additions & 2 deletions src/core/internal/string.d
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Original file line number Diff line number Diff line change
Expand Up @@ -78,8 +78,8 @@ auto signedToTempString(long value, char[] buf, uint radix) @safe
if(neg)
{
// about to do a slice without a bounds check
assert(r.ptr > buf.ptr);
r = (() @trusted => (r.ptr-1)[0..r.length+1])();
auto trustedSlice() @trusted { assert(r.ptr > buf.ptr); return (r.ptr-1)[0..r.length+1]; }
r = trustedSlice();
r[0] = '-';
}
return r;
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27 changes: 17 additions & 10 deletions src/rt/util/array.d
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Expand Up @@ -10,27 +10,28 @@ module rt.util.array;


import core.internal.string;
import core.stdc.stdint;


@safe /* pure dmd @@@BUG11461@@@ */ nothrow:

void enforceTypedArraysConformable(T)(in char[] action,
in T[] a1, in T[] a2, in bool allowOverlap = false)
void enforceTypedArraysConformable(T)(const char[] action,
const T[] a1, const T[] a2, in bool allowOverlap = false)
{
_enforceSameLength(action, a1.length, a2.length);
if(!allowOverlap)
_enforceNoOverlap(action, a1.ptr, a2.ptr, T.sizeof * a1.length);
_enforceNoOverlap(action, arrayToPtr(a1), arrayToPtr(a2), T.sizeof * a1.length);
}

void enforceRawArraysConformable(in char[] action, in size_t elementSize,
in void[] a1, in void[] a2, in bool allowOverlap = false)
void enforceRawArraysConformable(const char[] action, in size_t elementSize,
const void[] a1, const void[] a2, in bool allowOverlap = false)
{
_enforceSameLength(action, a1.length, a2.length);
if(!allowOverlap)
_enforceNoOverlap(action, a1.ptr, a2.ptr, elementSize * a1.length);
_enforceNoOverlap(action, arrayToPtr(a1), arrayToPtr(a2), elementSize * a1.length);
}

private void _enforceSameLength(in char[] action,
private void _enforceSameLength(const char[] action,
in size_t length1, in size_t length2)
{
if(length1 == length2)
Expand All @@ -46,10 +47,10 @@ private void _enforceSameLength(in char[] action,
throw new Error(msg);
}

private void _enforceNoOverlap(in char[] action,
in void* ptr1, in void* ptr2, in size_t bytes)
private void _enforceNoOverlap(const char[] action,
uintptr_t ptr1, uintptr_t ptr2, in size_t bytes)
{
const size_t d = ptr1 > ptr2 ? ptr1 - ptr2 : ptr2 - ptr1;
const d = ptr1 > ptr2 ? ptr1 - ptr2 : ptr2 - ptr1;
if(d >= bytes)
return;
const overlappedBytes = bytes - d;
Expand All @@ -63,3 +64,9 @@ private void _enforceNoOverlap(in char[] action,
msg ~= bytes.unsignedToTempString(tmpBuff, 10);
throw new Error(msg);
}

private uintptr_t arrayToPtr(const void[] array) @trusted
{
// Ok because the user will never dereference the pointer
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@yebblies yebblies Jun 12, 2016

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Not ok... If safe code can call this method and thereby break memory safety, it should not be trusted. The fact that the callers above don't do this is just a convention - they are effectively @trusted thanks to this function.

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@schveiguy schveiguy Jun 12, 2016

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What about this instead:

private size_t arrayToPtr(const void[] array) @trusted { return cast(size_t)array.ptr; }

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@schveiguy schveiguy Jun 12, 2016

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Hm... probably should return ptrdiff_t instead of size_t, since pointer arithmetic is signed.

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@yebblies yebblies Jun 12, 2016

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Sure, anything that prevents it from being dereferenced in @safe code.

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@schveiguy schveiguy Jun 12, 2016

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probably should return ptrdiff_t

I take it back, needs to be size_t because of the code in _enforceNoOverlap

return cast(uintptr_t)array.ptr;
}