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LibIPC: Close received IPC::File fd's by default unless taken

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When receiving a file descriptor over IPC, the receiver must now call
take_fd() on the IPC::File to take over the descriptor. Otherwise,
IPC::File will close the file on destruction.
This commit is contained in:
Andreas Kling 2021-01-14 09:31:21 +01:00
parent 384d047e3e
commit 7f2d8e8884
5 changed files with 50 additions and 5 deletions
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47
Userland/Libraries/LibIPC/File.h
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@ -1,5 +1,6 @@
/*
* Copyright (c) 2020, Sergey Bugaev <bugaevc@serenityos.org>
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -26,9 +27,15 @@
#pragma once
#include <AK/Noncopyable.h>
#include <AK/StdLibExtras.h>
#include <unistd.h>
namespace IPC {
class File {
AK_MAKE_NONCOPYABLE(File);
public:
// Must have a default constructor, because LibIPC
// default-constructs arguments prior to decoding them.
@ -40,10 +47,48 @@ public:
{
}
// Tagged constructor for fd's that should be closed on destruction unless take_fd() is called.
enum Tag {
ConstructWithReceivedFileDescriptor = 1,
};
File(int fd, Tag)
: m_fd(fd)
, m_close_on_destruction(true)
{
}
File(File&& other)
: m_fd(exchange(other.m_fd, -1))
, m_close_on_destruction(exchange(other.m_close_on_destruction, false))
{
}
File& operator=(File&& other)
{
if (this != &other) {
m_fd = exchange(other.m_fd, -1);
m_close_on_destruction = exchange(other.m_close_on_destruction, false);
}
return *this;
}
~File()
{
if (m_close_on_destruction && m_fd != -1)
close(m_fd);
}
int fd() const { return m_fd; }
// NOTE: This is 'const' since generated IPC messages expose all parameters by const reference.
[[nodiscard]] int take_fd() const
{
return exchange(m_fd, -1);
}
private:
int m_fd { -1 };
mutable int m_fd { -1 };
bool m_close_on_destruction { false };
};
}