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Kernel: Make copy_to/from_user safe and remove unnecessary checks

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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.
This commit is contained in:
Tom 2020-09-11 21:11:07 -06:00 • committed by Andreas Kling
parent 7d1b8417bd
commit c8d9f1b9c9
149 changed files with 1585 additions and 1244 deletions
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50
Kernel/Net/TCPSocket.cpp
View file

@ -161,7 +161,7 @@ NonnullRefPtr<TCPSocket> TCPSocket::create(int protocol)
return adopt(*new TCPSocket(protocol));
}
KResultOr<size_t> TCPSocket::protocol_receive(const KBuffer& packet_buffer, void* buffer, size_t buffer_size, int flags)
KResultOr<size_t> TCPSocket::protocol_receive(const KBuffer& packet_buffer, UserOrKernelBuffer& buffer, size_t buffer_size, int flags)
{
(void)flags;
auto& ipv4_packet = *(const IPv4Packet*)(packet_buffer.data());
@ -171,17 +171,20 @@ KResultOr<size_t> TCPSocket::protocol_receive(const KBuffer& packet_buffer, void
klog() << "payload_size " << payload_size << ", will it fit in " << buffer_size << "?";
#endif
ASSERT(buffer_size >= payload_size);
memcpy(buffer, tcp_packet.payload(), payload_size);
if (!buffer.write(tcp_packet.payload(), payload_size))
return KResult(-EFAULT);
return payload_size;
}
KResultOr<size_t> TCPSocket::protocol_send(const void* data, size_t data_length)
KResultOr<size_t> TCPSocket::protocol_send(const UserOrKernelBuffer& data, size_t data_length)
{
send_tcp_packet(TCPFlags::PUSH | TCPFlags::ACK, data, data_length);
int err = send_tcp_packet(TCPFlags::PUSH | TCPFlags::ACK, &data, data_length);
if (err < 0)
return KResult(err);
return data_length;
}
void TCPSocket::send_tcp_packet(u16 flags, const void* payload, size_t payload_size)
int TCPSocket::send_tcp_packet(u16 flags, const UserOrKernelBuffer* payload, size_t payload_size)
{
auto buffer = ByteBuffer::create_zeroed(sizeof(TCPPacket) + payload_size);
auto& tcp_packet = *(TCPPacket*)(buffer.data());
@ -196,31 +199,37 @@ void TCPSocket::send_tcp_packet(u16 flags, const void* payload, size_t payload_s
if (flags & TCPFlags::ACK)
tcp_packet.set_ack_number(m_ack_number);
if (payload && !payload->read(tcp_packet.payload(), payload_size))
return -EFAULT;
if (flags & TCPFlags::SYN) {
++m_sequence_number;
} else {
m_sequence_number += payload_size;
}
memcpy(tcp_packet.payload(), payload, payload_size);
tcp_packet.set_checksum(compute_tcp_checksum(local_address(), peer_address(), tcp_packet, payload_size));
if (tcp_packet.has_syn() || payload_size > 0) {
LOCKER(m_not_acked_lock);
m_not_acked.append({ m_sequence_number, move(buffer) });
send_outgoing_packets();
return;
return 0;
}
auto routing_decision = route_to(peer_address(), local_address(), bound_interface());
ASSERT(!routing_decision.is_zero());
routing_decision.adapter->send_ipv4(
auto packet_buffer = UserOrKernelBuffer::for_kernel_buffer(buffer.data());
int err = routing_decision.adapter->send_ipv4(
routing_decision.next_hop, peer_address(), IPv4Protocol::TCP,
buffer, ttl());
packet_buffer, buffer.size(), ttl());
if (err < 0)
return err;
m_packets_out++;
m_bytes_out += buffer.size();
return 0;
}
void TCPSocket::send_outgoing_packets()
@ -243,12 +252,17 @@ void TCPSocket::send_outgoing_packets()
auto& tcp_packet = *(TCPPacket*)(packet.buffer.data());
klog() << "sending tcp packet from " << local_address().to_string().characters() << ":" << local_port() << " to " << peer_address().to_string().characters() << ":" << peer_port() << " with (" << (tcp_packet.has_syn() ? "SYN " : "") << (tcp_packet.has_ack() ? "ACK " : "") << (tcp_packet.has_fin() ? "FIN " : "") << (tcp_packet.has_rst() ? "RST " : "") << ") seq_no=" << tcp_packet.sequence_number() << ", ack_no=" << tcp_packet.ack_number() << ", tx_counter=" << packet.tx_counter;
#endif
routing_decision.adapter->send_ipv4(
auto packet_buffer = UserOrKernelBuffer::for_kernel_buffer(packet.buffer.data());
int err = routing_decision.adapter->send_ipv4(
routing_decision.next_hop, peer_address(), IPv4Protocol::TCP,
packet.buffer, ttl());
m_packets_out++;
m_bytes_out += packet.buffer.size();
packet_buffer, packet.buffer.size(), ttl());
if (err < 0) {
auto& tcp_packet = *(TCPPacket*)(packet.buffer.data());
klog() << "Error (" << err << ") sending tcp packet from " << local_address().to_string().characters() << ":" << local_port() << " to " << peer_address().to_string().characters() << ":" << peer_port() << " with (" << (tcp_packet.has_syn() ? "SYN " : "") << (tcp_packet.has_ack() ? "ACK " : "") << (tcp_packet.has_fin() ? "FIN " : "") << (tcp_packet.has_rst() ? "RST " : "") << ") seq_no=" << tcp_packet.sequence_number() << ", ack_no=" << tcp_packet.ack_number() << ", tx_counter=" << packet.tx_counter;
} else {
m_packets_out++;
m_bytes_out += packet.buffer.size();
}
}
}
@ -366,7 +380,9 @@ KResult TCPSocket::protocol_connect(FileDescription& description, ShouldBlock sh
m_ack_number = 0;
set_setup_state(SetupState::InProgress);
send_tcp_packet(TCPFlags::SYN);
int err = send_tcp_packet(TCPFlags::SYN);
if (err < 0)
return KResult(err);
m_state = State::SynSent;
m_role = Role::Connecting;
m_direction = Direction::Outgoing;
@ -433,7 +449,7 @@ void TCPSocket::shut_down_for_writing()
#ifdef TCP_SOCKET_DEBUG
dbg() << " Sending FIN/ACK from Established and moving into FinWait1";
#endif
send_tcp_packet(TCPFlags::FIN | TCPFlags::ACK);
(void)send_tcp_packet(TCPFlags::FIN | TCPFlags::ACK);
set_state(State::FinWait1);
} else {
dbg() << " Shutting down TCPSocket for writing but not moving to FinWait1 since state is " << to_string(state());
@ -447,7 +463,7 @@ KResult TCPSocket::close()
#ifdef TCP_SOCKET_DEBUG
dbg() << " Sending FIN from CloseWait and moving into LastAck";
#endif
send_tcp_packet(TCPFlags::FIN | TCPFlags::ACK);
(void)send_tcp_packet(TCPFlags::FIN | TCPFlags::ACK);
set_state(State::LastAck);
}