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Kernel: Remove double-counting of allocated pages in AnonymousVMObject

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When constructing an AnonymousVMObject with the AllocateNow allocation
strategy we accidentally allocated the committed pages directly through
MemoryManager instead of taking them from our m_unused_physical_pages
CommittedPhysicalPageSet, which meant they were counted as allocated in
MemoryManager, but were still counted as unallocated in the PageSet,
who would then try to uncommit them on destruction, resulting in a
failed assertion.

To help prevent similar issues in the future a Badge<T> was added to
MM::allocate_committed_user_physical_page to prevent allocation of
commited pages not via a CommittedPhysicalPageSet.
This commit is contained in:
Idan Horowitz 2021-08-05 20:58:09 +03:00 committed by Andreas Kling
parent e8d10fb429
commit 3e909c0c49
Notes: sideshowbarker 2024-07-18 07:26:38 +09:00 
Author: https://github.com/IdanHo
Commit: https://github.com/SerenityOS/serenity/commit/3e909c0c49d
Pull-request: https://github.com/SerenityOS/serenity/pull/9226
3 changed files with 4 additions and 4 deletions
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2
Kernel/VM/AnonymousVMObject.cpp
View file

@ -131,7 +131,7 @@ AnonymousVMObject::AnonymousVMObject(size_t size, AllocationStrategy strategy, O
if (strategy == AllocationStrategy::AllocateNow) {
// Allocate all pages right now. We know we can get all because we committed the amount needed
for (size_t i = 0; i < page_count(); ++i)
physical_pages()[i] = MM.allocate_committed_user_physical_page(MemoryManager::ShouldZeroFill::Yes);
physical_pages()[i] = m_unused_committed_pages->take_one();
} else {
auto& initial_page = (strategy == AllocationStrategy::Reserve) ? MM.lazy_committed_page() : MM.shared_zero_page();
for (size_t i = 0; i < page_count(); ++i)

4
Kernel/VM/MemoryManager.cpp
View file

@ -840,7 +840,7 @@ RefPtr<PhysicalPage> MemoryManager::find_free_user_physical_page(bool committed)
return page;
}
NonnullRefPtr<PhysicalPage> MemoryManager::allocate_committed_user_physical_page(ShouldZeroFill should_zero_fill)
NonnullRefPtr<PhysicalPage> MemoryManager::allocate_committed_user_physical_page(Badge<CommittedPhysicalPageSet>, ShouldZeroFill should_zero_fill)
{
ScopedSpinLock lock(s_mm_lock);
auto page = find_free_user_physical_page(true);
@ -1134,7 +1134,7 @@ NonnullRefPtr<PhysicalPage> CommittedPhysicalPageSet::take_one()
{
VERIFY(m_page_count > 0);
--m_page_count;
return MM.allocate_committed_user_physical_page(MemoryManager::ShouldZeroFill::Yes);
return MM.allocate_committed_user_physical_page({}, MemoryManager::ShouldZeroFill::Yes);
}
void CommittedPhysicalPageSet::uncommit_one()

2
Kernel/VM/MemoryManager.h
View file

@ -174,7 +174,7 @@ public:
Optional<CommittedPhysicalPageSet> commit_user_physical_pages(size_t page_count);
void uncommit_user_physical_pages(Badge<CommittedPhysicalPageSet>, size_t page_count);
NonnullRefPtr<PhysicalPage> allocate_committed_user_physical_page(ShouldZeroFill = ShouldZeroFill::Yes);
NonnullRefPtr<PhysicalPage> allocate_committed_user_physical_page(Badge<CommittedPhysicalPageSet>, ShouldZeroFill = ShouldZeroFill::Yes);
RefPtr<PhysicalPage> allocate_user_physical_page(ShouldZeroFill = ShouldZeroFill::Yes, bool* did_purge = nullptr);
RefPtr<PhysicalPage> allocate_supervisor_physical_page();
NonnullRefPtrVector<PhysicalPage> allocate_contiguous_supervisor_physical_pages(size_t size);