diff options
| author | Dean Deng <deandeng@google.com> | 2020-05-27 18:18:17 -0700 |
|---|---|---|
| committer | gVisor bot <gvisor-bot@google.com> | 2020-05-27 18:19:38 -0700 |
| commit | 32021bce9607e09f3d21d3d28047d49340da231e (patch) | |
| tree | 94008e5ac3110fcbd88146879e4f622302eb2348 | |
| parent | 835e8c89a5e8ed0008821b1036ce3f507394dce5 (diff) | |
Correctly update link and ref counts in rmdir.
Inotify sends events when a watch target is reaches a link count of 0 (see
include/linux/fsnotify.h:fsnotify_inoderemove). Currently, we do not account
for both dir/ and dir/.. in unlink, causing
syscalls/linux/inotify.cc:WatchTargetDeletionGeneratesEvent to fail because
the expected inotify events are not generated.
Furthermore, we should DecRef() once the inode reaches zero links; otherwise,
we will leak a reference.
PiperOrigin-RevId: 313502091
| -rw-r--r-- | pkg/sentry/fsimpl/tmpfs/filesystem.go | 4 | ||||
| -rw-r--r-- | pkg/sentry/fsimpl/tmpfs/tmpfs.go | 15 |
2 files changed, 11 insertions, 8 deletions
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go index 80fa7b29d..7c04570f1 100644 --- a/pkg/sentry/fsimpl/tmpfs/filesystem.go +++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go @@ -603,8 +603,10 @@ func (fs *filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error return err } parentDir.removeChildLocked(child) - parentDir.inode.decLinksLocked() // from child's ".." + // Remove links for child, child/., and child/.. child.inode.decLinksLocked() + child.inode.decLinksLocked() + parentDir.inode.decLinksLocked() vfsObj.CommitDeleteDentry(&child.vfsd) parentDir.inode.touchCMtime() return nil diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go index 1e781aecd..b739095b7 100644 --- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go +++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go @@ -209,11 +209,9 @@ type inode struct { // refs is a reference count. refs is accessed using atomic memory // operations. // - // A reference is held on all inodes that are reachable in the filesystem - // tree. For non-directories (which may have multiple hard links), this - // means that a reference is dropped when nlink reaches 0. For directories, - // nlink never reaches 0 due to the "." entry; instead, - // filesystem.RmdirAt() drops the reference. + // A reference is held on all inodes as long as they are reachable in the + // filesystem tree, i.e. nlink is nonzero. This reference is dropped when + // nlink reaches 0. refs int64 // xattrs implements extended attributes. @@ -276,14 +274,17 @@ func (i *inode) incLinksLocked() { atomic.AddUint32(&i.nlink, 1) } -// decLinksLocked decrements i's link count. +// decLinksLocked decrements i's link count. If the link count reaches 0, we +// remove a reference on i as well. // // Preconditions: filesystem.mu must be locked for writing. i.nlink != 0. func (i *inode) decLinksLocked() { if i.nlink == 0 { panic("tmpfs.inode.decLinksLocked() called with no existing links") } - atomic.AddUint32(&i.nlink, ^uint32(0)) + if atomic.AddUint32(&i.nlink, ^uint32(0)) == 0 { + i.decRef() + } } func (i *inode) incRef() { |