Privatae
43 lines
1.3 KiB
Go
43 lines
1.3 KiB
Go
//go:build linux
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package main
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import (
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"os"
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"strconv"
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"golang.org/x/sys/unix"
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)
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// mcpOpenRegular opens path for reading only if what it names, after any
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// symlinks, is a regular file, without ever opening anything else. The first
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// open is O_PATH: it resolves the path and pins the inode but does not open
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// the file (no driver runs, a FIFO does not wait). Only once fstat says
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// regular is that same inode reopened for reading through /proc/self/fd, so
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// swapping the path between the look and the read reaches nothing new.
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func mcpOpenRegular(path string) (*os.File, string, error) {
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pfd, err := unix.Open(path, unix.O_PATH|unix.O_CLOEXEC, 0)
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if err != nil {
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return nil, "", &os.PathError{Op: "open", Path: path, Err: err}
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}
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defer unix.Close(pfd)
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var st unix.Stat_t
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if err := unix.Fstat(pfd, &st); err != nil {
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return nil, "", &os.PathError{Op: "fstat", Path: path, Err: err}
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}
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if st.Mode&unix.S_IFMT != unix.S_IFREG {
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return nil, "", errMCPNotRegular
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}
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fd, err := unix.Open("/proc/self/fd/"+strconv.Itoa(pfd), unix.O_RDONLY|unix.O_CLOEXEC|unix.O_NOCTTY|unix.O_NONBLOCK, 0)
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if err != nil {
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return nil, "", &os.PathError{Op: "reopen", Path: path, Err: err}
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}
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f := os.NewFile(uintptr(fd), path)
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fi, err := f.Stat()
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if err != nil || !fi.Mode().IsRegular() {
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f.Close()
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return nil, "", errMCPNotRegular
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}
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return f, mcpFileOwner(fi), nil
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}
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