Privatae
44 lines
1.4 KiB
Go
44 lines
1.4 KiB
Go
package main
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import (
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"errors"
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"strconv"
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"golang.org/x/sys/unix"
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)
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// openTreeEntry opens the entry name in the folder dfd with flags, for
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// packFolder.
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//
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// A folder is opened directly: with O_DIRECTORY the kernel refuses anything
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// that is not a folder before it opens it. Anything else is first opened as a
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// path only (O_PATH), which runs no driver code, so a device, pipe or terminal
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// swapped in since the look is never opened: opening some devices does
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// something by itself (a watchdog arms, a tape rewinds on close). Only a plain
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// file is then opened for reading, through /proc/self/fd, which reaches the
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// file the path fd holds and no other.
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func openTreeEntry(dfd int, name string, flags int) (int, error) {
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if flags&unix.O_DIRECTORY != 0 {
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return unix.Openat(dfd, name, flags, 0)
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}
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pfd, err := unix.Openat(dfd, name, unix.O_PATH|unix.O_NOFOLLOW|unix.O_CLOEXEC, 0)
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if err != nil {
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return -1, 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 -1, err
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}
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if st.Mode&unix.S_IFMT != unix.S_IFREG {
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return -1, errNotPlainFile
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}
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fd, err := unix.Open("/proc/self/fd/"+strconv.Itoa(pfd), flags&^unix.O_NOFOLLOW, 0)
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if errors.Is(err, unix.ENOENT) {
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// No /proc mounted: open by name as other systems do. packOpened
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// still checks that what was opened is the file that was looked at.
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return unix.Openat(dfd, name, flags, 0)
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}
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return fd, err
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}
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