diff options
Diffstat (limited to 'pkg/sentry/vfs')
| -rw-r--r-- | pkg/sentry/vfs/anonfs.go | 7 | ||||
| -rw-r--r-- | pkg/sentry/vfs/dentry.go | 32 | ||||
| -rw-r--r-- | pkg/sentry/vfs/inotify.go | 108 | ||||
| -rw-r--r-- | pkg/sentry/vfs/vfs.go | 3 |
4 files changed, 112 insertions, 38 deletions
diff --git a/pkg/sentry/vfs/anonfs.go b/pkg/sentry/vfs/anonfs.go index b7c6b60b8..746af03ec 100644 --- a/pkg/sentry/vfs/anonfs.go +++ b/pkg/sentry/vfs/anonfs.go @@ -301,7 +301,7 @@ func (d *anonDentry) DecRef() { // InotifyWithParent implements DentryImpl.InotifyWithParent. // // TODO(gvisor.dev/issue/1479): Implement inotify. -func (d *anonDentry) InotifyWithParent(events uint32, cookie uint32, et EventType) {} +func (d *anonDentry) InotifyWithParent(events, cookie uint32, et EventType) {} // Watches implements DentryImpl.Watches. // @@ -309,3 +309,8 @@ func (d *anonDentry) InotifyWithParent(events uint32, cookie uint32, et EventTyp func (d *anonDentry) Watches() *Watches { return nil } + +// OnZeroWatches implements Dentry.OnZeroWatches. +// +// TODO(gvisor.dev/issue/1479): Implement inotify. +func (d *anonDentry) OnZeroWatches() {} diff --git a/pkg/sentry/vfs/dentry.go b/pkg/sentry/vfs/dentry.go index 24af13eb1..cea3e6955 100644 --- a/pkg/sentry/vfs/dentry.go +++ b/pkg/sentry/vfs/dentry.go @@ -113,12 +113,29 @@ type DentryImpl interface { // // Note that the events may not actually propagate up to the user, depending // on the event masks. - InotifyWithParent(events uint32, cookie uint32, et EventType) + InotifyWithParent(events, cookie uint32, et EventType) // Watches returns the set of inotify watches for the file corresponding to // the Dentry. Dentries that are hard links to the same underlying file // share the same watches. + // + // Watches may return nil if the dentry belongs to a FilesystemImpl that + // does not support inotify. If an implementation returns a non-nil watch + // set, it must always return a non-nil watch set. Likewise, if an + // implementation returns a nil watch set, it must always return a nil watch + // set. + // + // The caller does not need to hold a reference on the dentry. Watches() *Watches + + // OnZeroWatches is called whenever the number of watches on a dentry drops + // to zero. This is needed by some FilesystemImpls (e.g. gofer) to manage + // dentry lifetime. + // + // The caller does not need to hold a reference on the dentry. OnZeroWatches + // may acquire inotify locks, so to prevent deadlock, no inotify locks should + // be held by the caller. + OnZeroWatches() } // IncRef increments d's reference count. @@ -149,17 +166,26 @@ func (d *Dentry) isMounted() bool { return atomic.LoadUint32(&d.mounts) != 0 } -// InotifyWithParent notifies all watches on the inodes for this dentry and +// InotifyWithParent notifies all watches on the targets represented by d and // its parent of events. -func (d *Dentry) InotifyWithParent(events uint32, cookie uint32, et EventType) { +func (d *Dentry) InotifyWithParent(events, cookie uint32, et EventType) { d.impl.InotifyWithParent(events, cookie, et) } // Watches returns the set of inotify watches associated with d. +// +// Watches will return nil if d belongs to a FilesystemImpl that does not +// support inotify. func (d *Dentry) Watches() *Watches { return d.impl.Watches() } +// OnZeroWatches performs cleanup tasks whenever the number of watches on a +// dentry drops to zero. +func (d *Dentry) OnZeroWatches() { + d.impl.OnZeroWatches() +} + // The following functions are exported so that filesystem implementations can // use them. The vfs package, and users of VFS, should not call these // functions. diff --git a/pkg/sentry/vfs/inotify.go b/pkg/sentry/vfs/inotify.go index 7fa7d2d0c..36e7a3767 100644 --- a/pkg/sentry/vfs/inotify.go +++ b/pkg/sentry/vfs/inotify.go @@ -49,9 +49,6 @@ const ( // Inotify represents an inotify instance created by inotify_init(2) or // inotify_init1(2). Inotify implements FileDescriptionImpl. // -// Lock ordering: -// Inotify.mu -> Watches.mu -> Inotify.evMu -// // +stateify savable type Inotify struct { vfsfd FileDescription @@ -122,17 +119,31 @@ func NewInotifyFD(ctx context.Context, vfsObj *VirtualFilesystem, flags uint32) // Release implements FileDescriptionImpl.Release. Release removes all // watches and frees all resources for an inotify instance. func (i *Inotify) Release() { + var ds []*Dentry // We need to hold i.mu to avoid a race with concurrent calls to // Inotify.handleDeletion from Watches. There's no risk of Watches // accessing this Inotify after the destructor ends, because we remove all // references to it below. i.mu.Lock() - defer i.mu.Unlock() for _, w := range i.watches { // Remove references to the watch from the watches set on the target. We // don't need to worry about the references from i.watches, since this // file description is about to be destroyed. - w.set.Remove(i.id) + d := w.target + ws := d.Watches() + // Watchable dentries should never return a nil watch set. + if ws == nil { + panic("Cannot remove watch from an unwatchable dentry") + } + ws.Remove(i.id) + if ws.Size() == 0 { + ds = append(ds, d) + } + } + i.mu.Unlock() + + for _, d := range ds { + d.OnZeroWatches() } } @@ -272,20 +283,19 @@ func (i *Inotify) queueEvent(ev *Event) { // newWatchLocked creates and adds a new watch to target. // -// Precondition: i.mu must be locked. -func (i *Inotify) newWatchLocked(target *Dentry, mask uint32) *Watch { - targetWatches := target.Watches() +// Precondition: i.mu must be locked. ws must be the watch set for target d. +func (i *Inotify) newWatchLocked(d *Dentry, ws *Watches, mask uint32) *Watch { w := &Watch{ - owner: i, - wd: i.nextWatchIDLocked(), - set: targetWatches, - mask: mask, + owner: i, + wd: i.nextWatchIDLocked(), + target: d, + mask: mask, } // Hold the watch in this inotify instance as well as the watch set on the // target. i.watches[w.wd] = w - targetWatches.Add(w) + ws.Add(w) return w } @@ -312,7 +322,9 @@ func (i *Inotify) handleDeletion(w *Watch) { // AddWatch constructs a new inotify watch and adds it to the target. It // returns the watch descriptor returned by inotify_add_watch(2). -func (i *Inotify) AddWatch(target *Dentry, mask uint32) int32 { +// +// The caller must hold a reference on target. +func (i *Inotify) AddWatch(target *Dentry, mask uint32) (int32, error) { // Note: Locking this inotify instance protects the result returned by // Lookup() below. With the lock held, we know for sure the lookup result // won't become stale because it's impossible for *this* instance to @@ -320,8 +332,14 @@ func (i *Inotify) AddWatch(target *Dentry, mask uint32) int32 { i.mu.Lock() defer i.mu.Unlock() + ws := target.Watches() + if ws == nil { + // While Linux supports inotify watches on all filesystem types, watches on + // filesystems like kernfs are not generally useful, so we do not. + return 0, syserror.EPERM + } // Does the target already have a watch from this inotify instance? - if existing := target.Watches().Lookup(i.id); existing != nil { + if existing := ws.Lookup(i.id); existing != nil { newmask := mask if mask&linux.IN_MASK_ADD != 0 { // "Add (OR) events to watch mask for this pathname if it already @@ -329,12 +347,12 @@ func (i *Inotify) AddWatch(target *Dentry, mask uint32) int32 { newmask |= atomic.LoadUint32(&existing.mask) } atomic.StoreUint32(&existing.mask, newmask) - return existing.wd + return existing.wd, nil } // No existing watch, create a new watch. - w := i.newWatchLocked(target, mask) - return w.wd + w := i.newWatchLocked(target, ws, mask) + return w.wd, nil } // RmWatch looks up an inotify watch for the given 'wd' and configures the @@ -353,9 +371,19 @@ func (i *Inotify) RmWatch(wd int32) error { delete(i.watches, wd) // Remove the watch from the watch target. - w.set.Remove(w.OwnerID()) + ws := w.target.Watches() + // AddWatch ensures that w.target has a non-nil watch set. + if ws == nil { + panic("Watched dentry cannot have nil watch set") + } + ws.Remove(w.OwnerID()) + remaining := ws.Size() i.mu.Unlock() + if remaining == 0 { + w.target.OnZeroWatches() + } + // Generate the event for the removal. i.queueEvent(newEvent(wd, "", linux.IN_IGNORED, 0)) @@ -374,6 +402,13 @@ type Watches struct { ws map[uint64]*Watch } +// Size returns the number of watches held by w. +func (w *Watches) Size() int { + w.mu.Lock() + defer w.mu.Unlock() + return len(w.ws) +} + // Lookup returns the watch owned by an inotify instance with the given id. // Returns nil if no such watch exists. // @@ -459,10 +494,6 @@ func (w *Watches) NotifyWithExclusions(name string, events, cookie uint32, et Ev func (w *Watches) HandleDeletion() { w.Notify("", linux.IN_DELETE_SELF, 0, InodeEvent) - // TODO(gvisor.dev/issue/1479): This doesn't work because maps are not copied - // by value. Ideally, we wouldn't have this circular locking so we can just - // notify of IN_DELETE_SELF in the same loop below. - // // We can't hold w.mu while calling watch.handleDeletion to preserve lock // ordering w.r.t to the owner inotify instances. Instead, atomically move // the watches map into a local variable so we can iterate over it safely. @@ -495,9 +526,8 @@ type Watch struct { // Descriptor for this watch. This is unique across an inotify instance. wd int32 - // set is the watch set containing this watch. It belongs to the target file - // of this watch. - set *Watches + // target is a dentry representing the watch target. Its watch set contains this watch. + target *Dentry // Events being monitored via this watch. Must be accessed with atomic // memory operations. @@ -606,7 +636,7 @@ func (e *Event) setName(name string) { func (e *Event) sizeOf() int { s := inotifyEventBaseSize + int(e.len) if s < inotifyEventBaseSize { - panic("overflow") + panic("Overflowed event size") } return s } @@ -676,11 +706,15 @@ func InotifyEventFromStatMask(mask uint32) uint32 { } // InotifyRemoveChild sends the appriopriate notifications to the watch sets of -// the child being removed and its parent. +// the child being removed and its parent. Note that unlike most pairs of +// parent/child notifications, the child is notified first in this case. func InotifyRemoveChild(self, parent *Watches, name string) { - self.Notify("", linux.IN_ATTRIB, 0, InodeEvent) - parent.Notify(name, linux.IN_DELETE, 0, InodeEvent) - // TODO(gvisor.dev/issue/1479): implement IN_EXCL_UNLINK. + if self != nil { + self.Notify("", linux.IN_ATTRIB, 0, InodeEvent) + } + if parent != nil { + parent.Notify(name, linux.IN_DELETE, 0, InodeEvent) + } } // InotifyRename sends the appriopriate notifications to the watch sets of the @@ -691,8 +725,14 @@ func InotifyRename(ctx context.Context, renamed, oldParent, newParent *Watches, dirEv = linux.IN_ISDIR } cookie := uniqueid.InotifyCookie(ctx) - oldParent.Notify(oldName, dirEv|linux.IN_MOVED_FROM, cookie, InodeEvent) - newParent.Notify(newName, dirEv|linux.IN_MOVED_TO, cookie, InodeEvent) + if oldParent != nil { + oldParent.Notify(oldName, dirEv|linux.IN_MOVED_FROM, cookie, InodeEvent) + } + if newParent != nil { + newParent.Notify(newName, dirEv|linux.IN_MOVED_TO, cookie, InodeEvent) + } // Somewhat surprisingly, self move events do not have a cookie. - renamed.Notify("", linux.IN_MOVE_SELF, 0, InodeEvent) + if renamed != nil { + renamed.Notify("", linux.IN_MOVE_SELF, 0, InodeEvent) + } } diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go index 9acca8bc7..58c7ad778 100644 --- a/pkg/sentry/vfs/vfs.go +++ b/pkg/sentry/vfs/vfs.go @@ -24,6 +24,9 @@ // Locks acquired by FilesystemImpls between Prepare{Delete,Rename}Dentry and Commit{Delete,Rename*}Dentry // VirtualFilesystem.filesystemsMu // EpollInstance.mu +// Inotify.mu +// Watches.mu +// Inotify.evMu // VirtualFilesystem.fsTypesMu // // Locking Dentry.mu in multiple Dentries requires holding |