Kernel: Make copy_to/from_user safe and remove unnecessary checks

Since the CPU already does almost all necessary validation steps
for us, we don't really need to attempt to do this. Doing it
ourselves doesn't really work very reliably, because we'd have to
account for other processors modifying virtual memory, and we'd
have to account for e.g. pages not being able to be allocated
due to insufficient resources.

So change the copy_to/from_user (and associated helper functions)
to use the new safe_memcpy, which will return whether it succeeded
or not. The only manual validation step needed (which the CPU
can't perform for us) is making sure the pointers provided by user
mode aren't pointing to kernel mappings.

To make it easier to read/write from/to either kernel or user mode
data add the UserOrKernelBuffer helper class, which will internally
either use copy_from/to_user or directly memcpy, or pass the data
through directly using a temporary buffer on the stack.

Last but not least we need to keep syscall params trivial as we
need to copy them from/to user mode using copy_from/to_user.

1 files changed, 3 insertions, 3 deletions

diff --git a/Kernel/Net/LocalSocket.h b/Kernel/Net/LocalSocket.h
index cafdf599a4..d39e78d20b 100644
--- a/Kernel/Net/LocalSocket.h
+++ b/Kernel/Net/LocalSocket.h
@@ -52,7 +52,7 @@ public:
 
     // ^Socket
     virtual KResult bind(Userspace<const sockaddr*>, socklen_t) override;
-    virtual KResult connect(FileDescription&, const sockaddr*, socklen_t, ShouldBlock = ShouldBlock::Yes) override;
+    virtual KResult connect(FileDescription&, Userspace<const sockaddr*>, socklen_t, ShouldBlock = ShouldBlock::Yes) override;
     virtual KResult listen(size_t) override;
     virtual void get_local_address(sockaddr*, socklen_t*) override;
     virtual void get_peer_address(sockaddr*, socklen_t*) override;
@@ -60,8 +60,8 @@ public:
     virtual void detach(FileDescription&) override;
     virtual bool can_read(const FileDescription&, size_t) const override;
     virtual bool can_write(const FileDescription&, size_t) const override;
-    virtual KResultOr<size_t> sendto(FileDescription&, const void*, size_t, int, Userspace<const sockaddr*>, socklen_t) override;
-    virtual KResultOr<size_t> recvfrom(FileDescription&, void*, size_t, int flags, Userspace<sockaddr*>, Userspace<socklen_t*>) override;
+    virtual KResultOr<size_t> sendto(FileDescription&, const UserOrKernelBuffer&, size_t, int, Userspace<const sockaddr*>, socklen_t) override;
+    virtual KResultOr<size_t> recvfrom(FileDescription&, UserOrKernelBuffer&, size_t, int flags, Userspace<sockaddr*>, Userspace<socklen_t*>) override;
     virtual KResult getsockopt(FileDescription&, int level, int option, Userspace<void*>, Userspace<socklen_t*>) override;
     virtual KResult chown(FileDescription&, uid_t, gid_t) override;
     virtual KResult chmod(FileDescription&, mode_t) override;