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Kernel: Implement some basic stack pointer validation

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VM regions can now be marked as stack regions, which is then validated
on syscall, and on page fault.

If a thread is caught with its stack pointer pointing into anything
that's *not* a Region with its stack bit set, we'll crash the whole
process with SIGSTKFLT.

Userspace must now allocate custom stacks by using mmap() with the new
MAP_STACK flag. This mechanism was first introduced in OpenBSD, and now
we have it too, yay! :^)
This commit is contained in:
Andreas Kling 2019-11-17 12:11:43 +01:00
parent 197ed1bb2a
commit 794758df3a
12 changed files with 101 additions and 5 deletions
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6
Kernel/VM/MemoryManager.cpp
View file

@ -549,6 +549,12 @@ void MemoryManager::unquickmap_page()
m_quickmap_in_use = false;
}
bool MemoryManager::validate_user_stack(const Process& process, VirtualAddress vaddr) const
{
auto* region = region_from_vaddr(process, vaddr);
return region && region->is_stack();
}
bool MemoryManager::validate_user_read(const Process& process, VirtualAddress vaddr) const
{
auto* region = region_from_vaddr(process, vaddr);