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4b2651ddab
The way the Process::FileDescriptions::allocate() API works today means that two callers who allocate back to back without associating a FileDescription with the allocated FD, will receive the same FD and thus one will stomp over the other. Naively tracking which FileDescriptions are allocated and moving onto the next would introduce other bugs however, as now if you "allocate" a fd and then return early further down the control flow of the syscall you would leak that fd. This change modifies this behavior by tracking which descriptions are allocated and then having an RAII type to "deallocate" the fd if the association is not setup the end of it's scope.
56 lines
1.7 KiB
C++
56 lines
1.7 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <Kernel/FileSystem/FIFO.h>
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#include <Kernel/FileSystem/FileDescription.h>
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#include <Kernel/Process.h>
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namespace Kernel {
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KResultOr<FlatPtr> Process::sys$pipe(int pipefd[2], int flags)
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{
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VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
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REQUIRE_PROMISE(stdio);
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if (fds().open_count() + 2 > fds().max_open())
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return EMFILE;
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// Reject flags other than O_CLOEXEC.
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if ((flags & O_CLOEXEC) != flags)
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return EINVAL;
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u32 fd_flags = (flags & O_CLOEXEC) ? FD_CLOEXEC : 0;
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auto fifo = FIFO::create(uid());
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auto open_reader_result = fifo->open_direction(FIFO::Direction::Reader);
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if (open_reader_result.is_error())
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return open_reader_result.error();
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auto open_writer_result = fifo->open_direction(FIFO::Direction::Writer);
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if (open_writer_result.is_error())
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return open_writer_result.error();
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auto reader_fd_or_error = m_fds.allocate();
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if (reader_fd_or_error.is_error())
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return reader_fd_or_error.error();
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auto reader_fd = reader_fd_or_error.release_value();
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m_fds[reader_fd.fd].set(open_reader_result.release_value(), fd_flags);
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m_fds[reader_fd.fd].description()->set_readable(true);
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if (!copy_to_user(&pipefd[0], &reader_fd.fd))
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return EFAULT;
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auto writer_fd_or_error = m_fds.allocate();
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if (writer_fd_or_error.is_error())
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return writer_fd_or_error.error();
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auto writer_fd = writer_fd_or_error.release_value();
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m_fds[writer_fd.fd].set(open_writer_result.release_value(), fd_flags);
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m_fds[writer_fd.fd].description()->set_writable(true);
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if (!copy_to_user(&pipefd[1], &writer_fd.fd))
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return EFAULT;
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return 0;
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}
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}
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