Kernel.Vmm: Fix potential race condition involving concurrent Allocate and Free calls (#3978)

* Avoid nullptr dereference on GetSocket

Was gonna include this in my socket PR, but that got merged before I could push this.

* Lock unmap mutex in PoolExpand and Allocate

PAYDAY 2 has a rare race condition involving dmem releases.
I'm not certain this commit will fix it, but this would cause a race condition that could cause asserts like what PAYDAY 2 can hit, so I'll just pray this does the job until I can prove it doesn't.
This commit is contained in:
Stephen Miller
2026-01-29 22:22:15 -06:00
committed by GitHub
parent 4f3aabd7af
commit 5bc4183e36
2 changed files with 5 additions and 2 deletions

View File

@@ -232,6 +232,9 @@ File* HandleTable::GetSocket(int d) {
return nullptr;
}
auto file = m_files.at(d);
if (!file) {
return nullptr;
}
if (file->type != Core::FileSys::FileType::Socket) {
return nullptr;
}

View File

@@ -177,7 +177,7 @@ bool MemoryManager::TryWriteBacking(void* address, const void* data, u64 size) {
}
PAddr MemoryManager::PoolExpand(PAddr search_start, PAddr search_end, u64 size, u64 alignment) {
std::scoped_lock lk{mutex};
std::scoped_lock lk{mutex, unmap_mutex};
alignment = alignment > 0 ? alignment : 64_KB;
auto dmem_area = FindDmemArea(search_start);
@@ -219,7 +219,7 @@ PAddr MemoryManager::PoolExpand(PAddr search_start, PAddr search_end, u64 size,
PAddr MemoryManager::Allocate(PAddr search_start, PAddr search_end, u64 size, u64 alignment,
s32 memory_type) {
std::scoped_lock lk{mutex};
std::scoped_lock lk{mutex, unmap_mutex};
alignment = alignment > 0 ? alignment : 16_KB;
auto dmem_area = FindDmemArea(search_start);