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https://github.com/opencontainers/runc.git
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Alexander Larsson
f6028219a5
Sometimes I was getting: 2014/06/13 13:47:24 finalize namespace drop bounding set read /proc/1/status: bad file descriptor This happens when applying the capabilities, and the code that reads the current caps opens /proc/1/status and then reads some data from it. But during this it gets a EBADFD error. The problem is that FinalizeNamespace() closes all FDs before applying the caps, and if a GC then happens after /proc/1/status is opened but before reading from the fd, then an old os.File finalizer may close the already closed-and-reused fd, wreaking havoc. We fix this by instead of closing the FDs we mark them close-on-exec which guarantees that they will be closed when we do the final exec into the container. Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
56 lines
1.4 KiB
Go
56 lines
1.4 KiB
Go
package utils
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import (
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"crypto/rand"
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"encoding/hex"
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"io"
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"io/ioutil"
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"path/filepath"
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"strconv"
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"syscall"
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)
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// GenerateRandomName returns a new name joined with a prefix. This size
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// specified is used to truncate the randomly generated value
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func GenerateRandomName(prefix string, size int) (string, error) {
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id := make([]byte, 32)
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if _, err := io.ReadFull(rand.Reader, id); err != nil {
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return "", err
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}
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return prefix + hex.EncodeToString(id)[:size], nil
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}
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// ResolveRootfs ensures that the current working directory is
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// not a symlink and returns the absolute path to the rootfs
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func ResolveRootfs(uncleanRootfs string) (string, error) {
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rootfs, err := filepath.Abs(uncleanRootfs)
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if err != nil {
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return "", err
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}
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return filepath.EvalSymlinks(rootfs)
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}
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func CloseExecFrom(minFd int) error {
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fdList, err := ioutil.ReadDir("/proc/self/fd")
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if err != nil {
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return err
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}
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for _, fi := range fdList {
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fd, err := strconv.Atoi(fi.Name())
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if err != nil {
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// ignore non-numeric file names
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continue
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}
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if fd < minFd {
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// ignore descriptors lower than our specified minimum
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continue
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}
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// intentionally ignore errors from syscall.CloseOnExec
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syscall.CloseOnExec(fd)
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// the cases where this might fail are basically file descriptors that have already been closed (including and especially the one that was created when ioutil.ReadDir did the "opendir" syscall)
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}
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return nil
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}
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