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SP: LargeAlloc return CBChunk & chase consequences

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Even if we opt not to bound these pointers internally (if they aren't headed out
to the user program or we later derive bounded pointers), they should still be
annotated as something other than CBArena, ensuring that we do not attempt to
use them for general amplification.
This commit is contained in:
Nathaniel Filardo
2021-04-01 13:20:17 +01:00
committed by Nathaniel Wesley Filardo
parent 54fec3821f
commit f7821e11eb
10 changed files with 175 additions and 126 deletions
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18
src/mem/slab.h
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@@ -1,6 +1,7 @@
#pragma once
#include "freelist.h"
#include "ptrhelpers.h"
#include "superslab.h"
#include <array>
@@ -20,7 +21,7 @@ namespace snmalloc
template<capptr_bounds B>
static CapPtr<Metaslab, B> get_meta(CapPtr<Slab, B> self)
{
static_assert(B == CBArena || B == CBChunk);
static_assert(B == CBArena || B == CBChunkD || B == CBChunk);
auto super = Superslab::get(self);
return super->get_meta(self);
@@ -102,8 +103,8 @@ namespace snmalloc
// bits. Note that this does remove the use from the meta slab, so it
// doesn't need doing on the slow path.
static SNMALLOC_FAST_PATH bool dealloc_fast(
CapPtr<Slab, CBArena> self,
CapPtr<Superslab, CBArena> super,
CapPtr<Slab, CBChunkD> self,
CapPtr<Superslab, CBChunkD> super,
CapPtr<FreeObject, CBArena> p,
LocalEntropy& entropy)
{
@@ -124,9 +125,9 @@ namespace snmalloc
// Returns a complex return code for managing the superslab meta data.
// i.e. This deallocation could make an entire superslab free.
static SNMALLOC_SLOW_PATH typename Superslab::Action dealloc_slow(
CapPtr<Slab, CBArena> self,
CapPtr<Slab, CBChunkD> self,
SlabList* sl,
CapPtr<Superslab, CBArena> super,
CapPtr<Superslab, CBChunkD> super,
CapPtr<FreeObject, CBArena> p,
LocalEntropy& entropy)
{
@@ -154,7 +155,12 @@ namespace snmalloc
allocated - meta->threshold_for_waking_slab(Metaslab::is_short(self));
// Push on the list of slabs for this sizeclass.
sl->insert_prev(meta.template as_static<SlabLink>());
// ChunkD-to-Chunk conversion might apply bounds, so we need to do so to
// the aligned object and then shift over to these bounds.
auto super_chunk = capptr_chunk_from_chunkd(super, SUPERSLAB_SIZE);
auto metalink = Aal::capptr_rebound(
super_chunk.as_void(), meta.template as_static<SlabLink>());
sl->insert_prev(metalink);
meta->debug_slab_invariant(self, entropy);
return Superslab::NoSlabReturn;
}