Kernel: Don't assert on PT_PEEK with kernelspace address

We were casting the address to Userspace<T> without validating it first
which is no good and will trap an assertion soon after.

Let's catch this sooner with an ASSERT in the Userspace<T> constructor
and update the PT_PEEK and PT_POKE handlers to avoid it.

Fixes #4505.

1 files changed, 8 insertions, 9 deletions

diff --git a/Kernel/Ptrace.cpp b/Kernel/Ptrace.cpp
index 61b6028670..656e200606 100644
--- a/Kernel/Ptrace.cpp
+++ b/Kernel/Ptrace.cpp
@@ -129,21 +129,20 @@ KResultOr<u32> handle_syscall(const Kernel::Syscall::SC_ptrace_params& params, P
         Kernel::Syscall::SC_ptrace_peek_params peek_params;
         if (!copy_from_user(&peek_params, reinterpret_cast<Kernel::Syscall::SC_ptrace_peek_params*>(params.addr)))
             return -EFAULT;
-
-        // read validation is done inside 'peek_user_data'
-        auto result = peer->process().peek_user_data((FlatPtr)peek_params.address);
-        if (result.is_error())
+        if (!is_user_address(VirtualAddress { peek_params.address }))
             return -EFAULT;
+        auto result = peer->process().peek_user_data(Userspace<const u32*> { (FlatPtr)peek_params.address });
+        if (result.is_error())
+            return result.error();
         if (!copy_to_user(peek_params.out_data, &result.value()))
             return -EFAULT;
         break;
     }
 
-    case PT_POKE: {
-        Userspace<u32*> addr = reinterpret_cast<FlatPtr>(params.addr);
-        // write validation is done inside 'poke_user_data'
-        return peer->process().poke_user_data(addr, params.data);
-    }
+    case PT_POKE:
+        if (!is_user_address(VirtualAddress { params.addr }))
+            return -EFAULT;
+        return peer->process().poke_user_data(Userspace<u32*> { (FlatPtr)params.addr }, params.data);
 
     default:
         return -EINVAL;