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Kernel: Add some basic double-kfree() detection

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Double kfree() is exceedingly rare in our kernel since we use automatic
memory management and smart pointers for almost all code. However, it
doesn't hurt to do some basic checking that might one day catch bugs.

This patch makes us VERIFY that we don't already consider the first
chunk of a kmalloc() allocation free when kfree()'ing it.
This commit is contained in:
Andreas Kling 2021-04-09 09:08:23 +02:00
parent fa9f5c9799
commit 79ebcacce2
1 changed files with 4 additions and 1 deletions
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5
Kernel/Heap/Heap.h
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@ -107,9 +107,12 @@ public:
return;
auto* a = (AllocationHeader*)((((u8*)ptr) - sizeof(AllocationHeader)));
VERIFY((u8*)a >= m_chunks && (u8*)ptr < m_chunks + m_total_chunks * CHUNK_SIZE);
VERIFY((u8*)a + a->allocation_size_in_chunks * CHUNK_SIZE <= m_chunks + m_total_chunks * CHUNK_SIZE);
FlatPtr start = ((FlatPtr)a - (FlatPtr)m_chunks) / CHUNK_SIZE;
// First, verify that the start of the allocation at `ptr` is actually allocated.
VERIFY(m_bitmap.get(start));
VERIFY((u8*)a + a->allocation_size_in_chunks * CHUNK_SIZE <= m_chunks + m_total_chunks * CHUNK_SIZE);
m_bitmap.set_range(start, a->allocation_size_in_chunks, false);
VERIFY(m_allocated_chunks >= a->allocation_size_in_chunks);