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dparse: Fix memory corruption #445

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Merged
Geod24 merged 1 commit into from
Jul 25, 2021
Merged

dparse: Fix memory corruption #445

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4 changes: 4 additions & 0 deletions src/dparse/rollback_allocator.d
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
module dparse.rollback_allocator;

import core.memory : GC;

//version = debug_rollback_allocator;

/**
Expand Down Expand Up @@ -147,6 +149,7 @@ private:
ubyte[] m = cast(ubyte[]) AlignedMallocator.instance.alignedAllocate(max(size + Node.sizeof, ALLOC_SIZE), memoryAlignment);
if (m is null)
onOutOfMemoryError();
GC.addRange(m.ptr, m.length);

version (debug_rollback_allocator)
m[] = 0;
Expand All @@ -164,6 +167,7 @@ private:
ubyte[] mem = (cast(ubyte*) first)[0 .. Node.sizeof + first.mem.length];
version (debug_rollback_allocator)
mem[] = 0;
GC.removeRange(mem.ptr);
AlignedMallocator.instance.deallocate(mem);
first = next;
}
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13 changes: 13 additions & 0 deletions src/dparse/stack_buffer.d
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
module dparse.stack_buffer;

import core.memory : GC;

import std.traits;

//version = debug_stack_allocator;
Expand All @@ -20,14 +22,21 @@ struct StackBuffer
static if (is(T == class))
static assert(T.sizeof == size_t.sizeof);

static if (hasIndirections!T)
while (_length % size_t.sizeof != 0)
put(ubyte(1));

if (arr.ptr != stackSpace.ptr)
{
if (_length + T.sizeof > arr.length)
{
size_t newLength = arr.length << 1;
while (_length + T.sizeof > newLength)
newLength <<= 1;
auto oldPtr = arr.ptr;
Mallocator.instance.reallocate(arr, newLength);
GC.removeRange(oldPtr);
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@CyberShadow CyberShadow Jul 24, 2021 •
edited
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I think there is a race condition here, which is unavoidable with the reallocate API.

We need to call removeRange after the data is copied, and after calling addRange on the new copy, but before the old buffer is deallocated. reallocate does both the copy and the deallocation together.

A bit surprising that stdx.allocator doesn't have a layer which calls addRange/removeRange, though maybe that kind of defeats the point of using custom allocators.

Also note that we can't make this call conditional on hasIndirections!T because T is just for the value being allocated right now, we don't know what the rest of the buffer contains, nor can we know if the buffer will be completely used for types without indirections.

GC.addRange(arr.ptr, arr.length);
version (debug_stack_allocator)
(cast(ubyte[]) arr)[_length .. $] = 0;
}
Expand All @@ -38,6 +47,7 @@ struct StackBuffer
while (_length + T.sizeof > newLength)
newLength <<= 1;
arr = Mallocator.instance.allocate(newLength);
GC.addRange(arr.ptr, arr.length);
version (debug_stack_allocator)
(cast(ubyte[]) arr)[] = 0;
arr[0 .. stackSpace.length] = stackSpace[];
Expand All @@ -54,7 +64,10 @@ struct StackBuffer
version (debug_stack_allocator)
(cast(ubyte[]) arr)[] = 0;
if (arr.ptr !is stackSpace.ptr)
{
GC.removeRange(arr.ptr);
Mallocator.instance.deallocate(arr);
}
}

void[] opSlice()
Expand Down