d6ea46ceda
Commit 7a7357dae1 ("LCOW: Implemented support for docker cp + build")
changed `container.BaseFS` from being a string (that could be empty but
can't lead to nil pointer dereference) to containerfs.ContainerFS,
which could be be `nil` and so nil dereference is at least theoretically
possible, which leads to panic (i.e. engine crashes).
Such a panic can be avoided by carefully analysing the source code in all
the places that dereference a variable, to make the variable can't be nil.
Practically, this analisys are impossible as code is constantly
evolving.
Still, we need to avoid panics and crashes. A good way to do so is to
explicitly check that a variable is non-nil, returning an error
otherwise. Even in case such a check looks absolutely redundant,
further changes to the code might make it useful, and having an
extra check is not a big price to pay to avoid a panic.
This commit adds such checks for all the places where it is not obvious
that container.BaseFS is not nil (which in this case means we do not
call daemon.Mount() a few lines earlier).
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
86 lines
2.9 KiB
Go
86 lines
2.9 KiB
Go
package container // import "github.com/docker/docker/container"
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import (
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"os"
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"github.com/docker/docker/api/types"
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"github.com/docker/docker/pkg/archive"
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"github.com/docker/docker/pkg/system"
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"github.com/pkg/errors"
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)
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// ResolvePath resolves the given path in the container to a resource on the
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// host. Returns a resolved path (absolute path to the resource on the host),
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// the absolute path to the resource relative to the container's rootfs, and
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// an error if the path points to outside the container's rootfs.
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func (container *Container) ResolvePath(path string) (resolvedPath, absPath string, err error) {
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if container.BaseFS == nil {
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return "", "", errors.New("ResolvePath: BaseFS of container " + container.ID + " is unexpectedly nil")
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}
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// Check if a drive letter supplied, it must be the system drive. No-op except on Windows
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path, err = system.CheckSystemDriveAndRemoveDriveLetter(path, container.BaseFS)
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if err != nil {
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return "", "", err
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}
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// Consider the given path as an absolute path in the container.
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absPath = archive.PreserveTrailingDotOrSeparator(
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container.BaseFS.Join(string(container.BaseFS.Separator()), path),
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path,
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container.BaseFS.Separator())
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// Split the absPath into its Directory and Base components. We will
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// resolve the dir in the scope of the container then append the base.
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dirPath, basePath := container.BaseFS.Split(absPath)
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resolvedDirPath, err := container.GetResourcePath(dirPath)
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if err != nil {
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return "", "", err
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}
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// resolvedDirPath will have been cleaned (no trailing path separators) so
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// we can manually join it with the base path element.
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resolvedPath = resolvedDirPath + string(container.BaseFS.Separator()) + basePath
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return resolvedPath, absPath, nil
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}
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// StatPath is the unexported version of StatPath. Locks and mounts should
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// be acquired before calling this method and the given path should be fully
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// resolved to a path on the host corresponding to the given absolute path
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// inside the container.
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func (container *Container) StatPath(resolvedPath, absPath string) (stat *types.ContainerPathStat, err error) {
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if container.BaseFS == nil {
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return nil, errors.New("StatPath: BaseFS of container " + container.ID + " is unexpectedly nil")
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}
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driver := container.BaseFS
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lstat, err := driver.Lstat(resolvedPath)
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if err != nil {
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return nil, err
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}
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var linkTarget string
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if lstat.Mode()&os.ModeSymlink != 0 {
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// Fully evaluate the symlink in the scope of the container rootfs.
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hostPath, err := container.GetResourcePath(absPath)
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if err != nil {
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return nil, err
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}
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linkTarget, err = driver.Rel(driver.Path(), hostPath)
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if err != nil {
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return nil, err
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}
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// Make it an absolute path.
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linkTarget = driver.Join(string(driver.Separator()), linkTarget)
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}
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return &types.ContainerPathStat{
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Name: driver.Base(absPath),
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Size: lstat.Size(),
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Mode: lstat.Mode(),
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Mtime: lstat.ModTime(),
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LinkTarget: linkTarget,
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}, nil
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}
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