diff options
author | Ayush Ranjan <ayushranjan@google.com> | 2020-08-07 20:06:39 -0700 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2020-08-07 20:08:47 -0700 |
commit | 3be26a271cd0fc9618fbcb34e1a2a84c4f234c86 (patch) | |
tree | 1ff6717aae2104543670375cb9c90010b2efccf4 /runsc | |
parent | 977618c8e155c0178979ff9f8ea05bbb5c0886b5 (diff) |
[vfs2] Fix tmpfs mounting.
Earlier we were using NLink to decide if /tmp is empty or not. However, NLink
at best tells us about the number of subdirectories (via the ".." entries).
NLink = n + 2 for n subdirectories. But it does not tell us if the directory is
empty. There still might be non-directory files. We could also not rely on
NLink because host overlayfs always returned 1.
VFS1 uses Readdir to decide if the directory is empty. Used a similar approach.
We now use IterDirents to decide if the "/tmp" directory is empty.
Fixes #3369
PiperOrigin-RevId: 325554234
Diffstat (limited to 'runsc')
-rw-r--r-- | runsc/boot/vfs.go | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/runsc/boot/vfs.go b/runsc/boot/vfs.go index e7d6035bb..08dce8b6c 100644 --- a/runsc/boot/vfs.go +++ b/runsc/boot/vfs.go @@ -400,21 +400,28 @@ func (c *containerMounter) mountTmpVFS2(ctx context.Context, conf *Config, creds Path: fspath.Parse("/tmp"), } // TODO(gvisor.dev/issue/2782): Use O_PATH when available. - statx, err := c.k.VFS().StatAt(ctx, creds, &pop, &vfs.StatOptions{}) + fd, err := c.k.VFS().OpenAt(ctx, creds, &pop, &vfs.OpenOptions{Flags: linux.O_RDONLY | linux.O_DIRECTORY}) switch err { case nil: - // Found '/tmp' in filesystem, check if it's empty. - if linux.FileMode(statx.Mode).FileType() != linux.ModeDirectory { - // Not a dir?! Leave it be. + defer fd.DecRef(ctx) + + err := fd.IterDirents(ctx, vfs.IterDirentsCallbackFunc(func(dirent vfs.Dirent) error { + if dirent.Name != "." && dirent.Name != ".." { + return syserror.ENOTEMPTY + } return nil - } - if statx.Nlink > 2 { + })) + switch err { + case nil: + log.Infof(`Mounting internal tmpfs on top of empty "/tmp"`) + case syserror.ENOTEMPTY: // If more than "." and ".." is found, skip internal tmpfs to prevent // hiding existing files. log.Infof(`Skipping internal tmpfs mount for "/tmp" because it's not empty`) return nil + default: + return err } - log.Infof(`Mounting internal tmpfs on top of empty "/tmp"`) fallthrough case syserror.ENOENT: @@ -429,8 +436,12 @@ func (c *containerMounter) mountTmpVFS2(ctx context.Context, conf *Config, creds } return c.mountSubmountVFS2(ctx, conf, mns, creds, &mountAndFD{Mount: tmpMount}) + case syserror.ENOTDIR: + // Not a dir?! Let it be. + return nil + default: - return fmt.Errorf(`stating "/tmp" inside container: %w`, err) + return fmt.Errorf(`opening "/tmp" inside container: %w`, err) } } |