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Kernel: Validate the full range of user memory passed to syscalls

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We now validate the full range of userspace memory passed into syscalls
instead of just checking that the first and last byte of the memory are
in process-owned regions.

This fixes an issue where it was possible to avoid rejection of invalid
addresses that sat between two valid ones, simply by passing a valid
address and a size large enough to put the end of the range at another
valid address.

I added a little test utility that tries to provoke EFAULT in various
ways to help verify this. I'm sure we can think of more ways to test
this but it's at least a start. :^)

Thanks to mozjag for pointing out that this code was still lacking!

Incidentally this also makes backtraces work again.

Fixes #989.
This commit is contained in:
Andreas Kling 2020-01-02 02:09:25 +01:00
parent e5ffa960d7
commit 3dcec260ed
4 changed files with 121 additions and 25 deletions
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11
Kernel/VM/MemoryManager.h
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@ -45,8 +45,10 @@ public:
void enter_process_paging_scope(Process&);
bool validate_user_stack(const Process&, VirtualAddress) const;
bool validate_user_read(const Process&, VirtualAddress) const;
bool validate_user_write(const Process&, VirtualAddress) const;
bool validate_user_read(const Process&, VirtualAddress, size_t) const;
bool validate_user_write(const Process&, VirtualAddress, size_t) const;
bool validate_kernel_read(const Process&, VirtualAddress, size_t) const;
enum class ShouldZeroFill {
No,
@ -85,6 +87,11 @@ private:
MemoryManager(u32 physical_address_for_kernel_page_tables);
~MemoryManager();
enum class AccessSpace { Kernel, User };
enum class AccessType { Read, Write };
template<AccessSpace, AccessType>
bool validate_range(const Process&, VirtualAddress, size_t) const;
void register_vmobject(VMObject&);
void unregister_vmobject(VMObject&);
void register_region(Region&);