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Rewrite copy-up to use buildah Copier

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The old copy-up implementation was very unhappy with symlinks,
which could cause containers to fail to start for unclear reasons
when a directory we wanted to copy-up contained one. Rewrite to
use the Buildah Copier, which is more recent and should be both
safer and less likely to blow up over links.

At the same time, fix a deadlock in copy-up for volumes requiring
mounting - the Mountpoint() function tried to take the
already-acquired volume lock.

Fixes #6003

Signed-off-by: Matthew Heon <mheon@redhat.com>
This commit is contained in:
Matthew Heon
2021-02-10 09:46:12 -05:00
parent 763d522983
commit ea910fc535
4 changed files with 79 additions and 44 deletions
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75
libpod/container_internal.go
View File

@ -13,6 +13,7 @@ import (
"strings"
"time"
"github.com/containers/buildah/copier"
"github.com/containers/common/pkg/secrets"
"github.com/containers/podman/v2/libpod/define"
"github.com/containers/podman/v2/libpod/events"
@ -1582,18 +1583,8 @@ func (c *Container) mountNamedVolume(v *ContainerNamedVolume, mountpoint string)
return nil, err
}
// HACK HACK HACK - copy up into a volume driver is 100% broken
// right now.
if vol.UsesVolumeDriver() {
logrus.Infof("Not copying up into volume %s as it uses a volume driver", vol.Name())
return vol, nil
}
// If the volume is not empty, we should not copy up.
volMount, err := vol.MountPoint()
if err != nil {
return nil, err
}
volMount := vol.mountPoint()
contents, err := ioutil.ReadDir(volMount)
if err != nil {
return nil, errors.Wrapf(err, "error listing contents of volume %s mountpoint when copying up from container %s", vol.Name(), c.ID())
@ -1609,8 +1600,55 @@ func (c *Container) mountNamedVolume(v *ContainerNamedVolume, mountpoint string)
if err != nil {
return nil, errors.Wrapf(err, "error calculating destination path to copy up container %s volume %s", c.ID(), vol.Name())
}
if err := c.copyWithTarFromImage(srcDir, volMount); err != nil && !os.IsNotExist(err) {
return nil, errors.Wrapf(err, "error copying content from container %s into volume %s", c.ID(), vol.Name())
// Do a manual stat on the source directory to verify existence.
// Skip the rest if it exists.
// TODO: Should this be stat or lstat? I'm using lstat because I
// think copy-up doesn't happen when the source is a link.
srcStat, err := os.Lstat(srcDir)
if err != nil {
if os.IsNotExist(err) {
// Source does not exist, don't bother copying
// up.
return vol, nil
}
return nil, errors.Wrapf(err, "error identifying source directory for copy up into volume %s", vol.Name())
}
// If it's not a directory we're mounting over it.
if !srcStat.IsDir() {
return vol, nil
}
// Buildah Copier accepts a reader, so we'll need a pipe.
reader, writer := io.Pipe()
defer reader.Close()
errChan := make(chan error, 1)
logrus.Infof("About to copy up into volume %s", vol.Name())
// Copy, container side: get a tar archive of what needs to be
// streamed into the volume.
go func() {
defer writer.Close()
getOptions := copier.GetOptions{
KeepDirectoryNames: false,
}
errChan <- copier.Get(mountpoint, "", getOptions, []string{v.Dest + "/."}, writer)
}()
// Copy, volume side: stream what we've written to the pipe, into
// the volume.
copyOpts := copier.PutOptions{}
if err := copier.Put(volMount, "", copyOpts, reader); err != nil {
err2 := <-errChan
if err2 != nil {
logrus.Errorf("Error streaming contents of container %s directory for volume copy-up: %v", c.ID(), err2)
}
return nil, errors.Wrapf(err, "error copying up to volume %s", vol.Name())
}
if err := <-errChan; err != nil {
return nil, errors.Wrapf(err, "error streaming container content for copy up into volume %s", vol.Name())
}
}
return vol, nil
@ -2060,17 +2098,6 @@ func (c *Container) unmount(force bool) error {
return nil
}
// this should be from chrootarchive.
// Container MUST be mounted before calling.
func (c *Container) copyWithTarFromImage(source, dest string) error {
mappings := idtools.NewIDMappingsFromMaps(c.config.IDMappings.UIDMap, c.config.IDMappings.GIDMap)
a := archive.NewArchiver(mappings)
if err := c.copyOwnerAndPerms(source, dest); err != nil {
return err
}
return a.CopyWithTar(source, dest)
}
// checkReadyForRemoval checks whether the given container is ready to be
// removed.
// These checks are only used if force-remove is not specified.