Add checklocks analyzer.

This validates that struct fields if annotated with "// checklocks:mu" where
"mu" is a mutex field in the same struct then access to the field is only
done with "mu" locked.

All types that are guarded by a mutex must be annotated with

// +checklocks:<mutex field name>

For more details please refer to README.md.

PiperOrigin-RevId: 360729328

6 files changed, 88 insertions, 72 deletions

diff --git a/pkg/sentry/fs/copy_up.go b/pkg/sentry/fs/copy_up.go
index 8e0aa9019..58deb25fc 100644
--- a/pkg/sentry/fs/copy_up.go
+++ b/pkg/sentry/fs/copy_up.go
@@ -303,17 +303,18 @@ func copyUpLocked(ctx context.Context, parent *Dirent, next *Dirent) error {
 
 	// Take a reference on the upper Inode (transferred to
 	// next.Inode.overlay.upper) and make new translations use it.
-	next.Inode.overlay.dataMu.Lock()
+	overlay := next.Inode.overlay
+	overlay.dataMu.Lock()
 	childUpperInode.IncRef()
-	next.Inode.overlay.upper = childUpperInode
-	next.Inode.overlay.dataMu.Unlock()
+	overlay.upper = childUpperInode
+	overlay.dataMu.Unlock()
 
 	// Invalidate existing translations through the lower Inode.
-	next.Inode.overlay.mappings.InvalidateAll(memmap.InvalidateOpts{})
+	overlay.mappings.InvalidateAll(memmap.InvalidateOpts{})
 
 	// Remove existing memory mappings from the lower Inode.
 	if lowerMappable != nil {
-		for seg := next.Inode.overlay.mappings.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
+		for seg := overlay.mappings.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
 			for m := range seg.Value() {
 				lowerMappable.RemoveMapping(ctx, m.MappingSpace, m.AddrRange, seg.Start(), m.Writable)
 			}
diff --git a/pkg/sentry/fs/gofer/inode_state.go b/pkg/sentry/fs/gofer/inode_state.go
index 141e3c27f..e2af1d2ae 100644
--- a/pkg/sentry/fs/gofer/inode_state.go
+++ b/pkg/sentry/fs/gofer/inode_state.go
@@ -109,6 +109,7 @@ func (i *inodeFileState) loadLoading(_ struct{}) {
 }
 
 // afterLoad is invoked by stateify.
+// +checklocks:i.loading
 func (i *inodeFileState) afterLoad() {
 	load := func() (err error) {
 		// See comment on i.loading().
diff --git a/pkg/sentry/fsimpl/overlay/filesystem.go b/pkg/sentry/fsimpl/overlay/filesystem.go
index f7f795b10..917709d75 100644
--- a/pkg/sentry/fsimpl/overlay/filesystem.go
+++ b/pkg/sentry/fsimpl/overlay/filesystem.go
@@ -85,6 +85,8 @@ func putDentrySlice(ds *[]*dentry) {
 // but dentry slices are allocated lazily, and it's much easier to say "defer
 // fs.renameMuRUnlockAndCheckDrop(&ds)" than "defer func() {
 // fs.renameMuRUnlockAndCheckDrop(ds) }()" to work around this.
+//
+// +checklocks:fs.renameMu
 func (fs *filesystem) renameMuRUnlockAndCheckDrop(ctx context.Context, dsp **[]*dentry) {
 	fs.renameMu.RUnlock()
 	if *dsp == nil {
@@ -110,6 +112,7 @@ func (fs *filesystem) renameMuRUnlockAndCheckDrop(ctx context.Context, dsp **[]*
 	putDentrySlice(*dsp)
 }
 
+// +checklocks:fs.renameMu
 func (fs *filesystem) renameMuUnlockAndCheckDrop(ctx context.Context, ds **[]*dentry) {
 	if *ds == nil {
 		fs.renameMu.Unlock()
diff --git a/pkg/sentry/pgalloc/pgalloc.go b/pkg/sentry/pgalloc/pgalloc.go
index 58cc11a13..a4af3e21b 100644
--- a/pkg/sentry/pgalloc/pgalloc.go
+++ b/pkg/sentry/pgalloc/pgalloc.go
@@ -876,6 +876,7 @@ func (f *MemoryFile) UpdateUsage() error {
 // in bs, sets committed[i] to 1 if the page is committed and 0 otherwise.
 //
 // Precondition: f.mu must be held; it may be unlocked and reacquired.
+// +checklocks:f.mu
 func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func(bs []byte, committed []byte) error) error {
 	// Track if anything changed to elide the merge. In the common case, we
 	// expect all segments to be committed and no merge to occur.
@@ -925,72 +926,73 @@ func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func(
 		r := seg.Range()
 
 		var checkErr error
-		err := f.forEachMappingSlice(r, func(s []byte) {
-			if checkErr != nil {
-				return
-			}
-
-			// Ensure that we have sufficient buffer for the call
-			// (one byte per page). The length of each slice must
-			// be page-aligned.
-			bufLen := len(s) / usermem.PageSize
-			if len(buf) < bufLen {
-				buf = make([]byte, bufLen)
-			}
+		err := f.forEachMappingSlice(r,
+			func(s []byte) {
+				if checkErr != nil {
+					return
+				}
 
-			// Query for new pages in core.
-			// NOTE(b/165896008): mincore (which is passed as checkCommitted)
-			// by f.UpdateUsage() might take a really long time. So unlock f.mu
-			// while checkCommitted runs.
-			f.mu.Unlock()
-			err := checkCommitted(s, buf)
-			f.mu.Lock()
-			if err != nil {
-				checkErr = err
-				return
-			}
+				// Ensure that we have sufficient buffer for the call
+				// (one byte per page). The length of each slice must
+				// be page-aligned.
+				bufLen := len(s) / usermem.PageSize
+				if len(buf) < bufLen {
+					buf = make([]byte, bufLen)
+				}
 
-			// Scan each page and switch out segments.
-			seg := f.usage.LowerBoundSegment(r.Start)
-			for i := 0; i < bufLen; {
-				if buf[i]&0x1 == 0 {
-					i++
-					continue
+				// Query for new pages in core.
+				// NOTE(b/165896008): mincore (which is passed as checkCommitted)
+				// by f.UpdateUsage() might take a really long time. So unlock f.mu
+				// while checkCommitted runs.
+				f.mu.Unlock()
+				err := checkCommitted(s, buf)
+				f.mu.Lock()
+				if err != nil {
+					checkErr = err
+					return
 				}
-				// Scan to the end of this committed range.
-				j := i + 1
-				for ; j < bufLen; j++ {
-					if buf[j]&0x1 == 0 {
-						break
+
+				// Scan each page and switch out segments.
+				seg := f.usage.LowerBoundSegment(r.Start)
+				for i := 0; i < bufLen; {
+					if buf[i]&0x1 == 0 {
+						i++
+						continue
 					}
-				}
-				committedFR := memmap.FileRange{
-					Start: r.Start + uint64(i*usermem.PageSize),
-					End:   r.Start + uint64(j*usermem.PageSize),
-				}
-				// Advance seg to committedFR.Start.
-				for seg.Ok() && seg.End() < committedFR.Start {
-					seg = seg.NextSegment()
-				}
-				// Mark pages overlapping committedFR as committed.
-				for seg.Ok() && seg.Start() < committedFR.End {
-					if seg.ValuePtr().canCommit() {
-						seg = f.usage.Isolate(seg, committedFR)
-						seg.ValuePtr().knownCommitted = true
-						amount := seg.Range().Length()
-						usage.MemoryAccounting.Inc(amount, seg.ValuePtr().kind)
-						f.usageExpected += amount
-						changedAny = true
+					// Scan to the end of this committed range.
+					j := i + 1
+					for ; j < bufLen; j++ {
+						if buf[j]&0x1 == 0 {
+							break
+						}
 					}
-					seg = seg.NextSegment()
+					committedFR := memmap.FileRange{
+						Start: r.Start + uint64(i*usermem.PageSize),
+						End:   r.Start + uint64(j*usermem.PageSize),
+					}
+					// Advance seg to committedFR.Start.
+					for seg.Ok() && seg.End() < committedFR.Start {
+						seg = seg.NextSegment()
+					}
+					// Mark pages overlapping committedFR as committed.
+					for seg.Ok() && seg.Start() < committedFR.End {
+						if seg.ValuePtr().canCommit() {
+							seg = f.usage.Isolate(seg, committedFR)
+							seg.ValuePtr().knownCommitted = true
+							amount := seg.Range().Length()
+							usage.MemoryAccounting.Inc(amount, seg.ValuePtr().kind)
+							f.usageExpected += amount
+							changedAny = true
+						}
+						seg = seg.NextSegment()
+					}
+					// Continue scanning for committed pages.
+					i = j + 1
 				}
-				// Continue scanning for committed pages.
-				i = j + 1
-			}
 
-			// Advance r.Start.
-			r.Start += uint64(len(s))
-		})
+				// Advance r.Start.
+				r.Start += uint64(len(s))
+			})
 		if checkErr != nil {
 			return checkErr
 		}
diff --git a/pkg/sentry/vfs/dentry.go b/pkg/sentry/vfs/dentry.go
index 320ab7ce1..e7ca24d96 100644
--- a/pkg/sentry/vfs/dentry.go
+++ b/pkg/sentry/vfs/dentry.go
@@ -211,12 +211,14 @@ func (vfs *VirtualFilesystem) PrepareDeleteDentry(mntns *MountNamespace, d *Dent
 
 // AbortDeleteDentry must be called after PrepareDeleteDentry if the deletion
 // fails.
+// +checklocks:d.mu
 func (vfs *VirtualFilesystem) AbortDeleteDentry(d *Dentry) {
 	d.mu.Unlock()
 }
 
 // CommitDeleteDentry must be called after PrepareDeleteDentry if the deletion
 // succeeds.
+// +checklocks:d.mu
 func (vfs *VirtualFilesystem) CommitDeleteDentry(ctx context.Context, d *Dentry) {
 	d.dead = true
 	d.mu.Unlock()
@@ -270,6 +272,8 @@ func (vfs *VirtualFilesystem) PrepareRenameDentry(mntns *MountNamespace, from, t
 
 // AbortRenameDentry must be called after PrepareRenameDentry if the rename
 // fails.
+// +checklocks:from.mu
+// +checklocks:to.mu
 func (vfs *VirtualFilesystem) AbortRenameDentry(from, to *Dentry) {
 	from.mu.Unlock()
 	if to != nil {
@@ -282,6 +286,8 @@ func (vfs *VirtualFilesystem) AbortRenameDentry(from, to *Dentry) {
 // that was replaced by from.
 //
 // Preconditions: PrepareRenameDentry was previously called on from and to.
+// +checklocks:from.mu
+// +checklocks:to.mu
 func (vfs *VirtualFilesystem) CommitRenameReplaceDentry(ctx context.Context, from, to *Dentry) {
 	from.mu.Unlock()
 	if to != nil {
@@ -297,6 +303,8 @@ func (vfs *VirtualFilesystem) CommitRenameReplaceDentry(ctx context.Context, fro
 // from and to are exchanged by rename(RENAME_EXCHANGE).
 //
 // Preconditions: PrepareRenameDentry was previously called on from and to.
+// +checklocks:from.mu
+// +checklocks:to.mu
 func (vfs *VirtualFilesystem) CommitRenameExchangeDentry(from, to *Dentry) {
 	from.mu.Unlock()
 	to.mu.Unlock()
diff --git a/pkg/sentry/vfs/mount.go b/pkg/sentry/vfs/mount.go
index 7063066ff..bac9eb905 100644
--- a/pkg/sentry/vfs/mount.go
+++ b/pkg/sentry/vfs/mount.go
@@ -217,20 +217,21 @@ func (vfs *VirtualFilesystem) ConnectMountAt(ctx context.Context, creds *auth.Cr
 		return err
 	}
 	vfs.mountMu.Lock()
-	vd.dentry.mu.Lock()
+	vdDentry := vd.dentry
+	vdDentry.mu.Lock()
 	for {
-		if vd.dentry.dead {
-			vd.dentry.mu.Unlock()
+		if vdDentry.dead {
+			vdDentry.mu.Unlock()
 			vfs.mountMu.Unlock()
 			vd.DecRef(ctx)
 			return syserror.ENOENT
 		}
 		// vd might have been mounted over between vfs.GetDentryAt() and
 		// vfs.mountMu.Lock().
-		if !vd.dentry.isMounted() {
+		if !vdDentry.isMounted() {
 			break
 		}
-		nextmnt := vfs.mounts.Lookup(vd.mount, vd.dentry)
+		nextmnt := vfs.mounts.Lookup(vd.mount, vdDentry)
 		if nextmnt == nil {
 			break
 		}
@@ -243,13 +244,13 @@ func (vfs *VirtualFilesystem) ConnectMountAt(ctx context.Context, creds *auth.Cr
 		}
 		// This can't fail since we're holding vfs.mountMu.
 		nextmnt.root.IncRef()
-		vd.dentry.mu.Unlock()
+		vdDentry.mu.Unlock()
 		vd.DecRef(ctx)
 		vd = VirtualDentry{
 			mount:  nextmnt,
 			dentry: nextmnt.root,
 		}
-		vd.dentry.mu.Lock()
+		vdDentry.mu.Lock()
 	}
 	// TODO(gvisor.dev/issue/1035): Linux requires that either both the mount
 	// point and the mount root are directories, or neither are, and returns
@@ -258,7 +259,7 @@ func (vfs *VirtualFilesystem) ConnectMountAt(ctx context.Context, creds *auth.Cr
 	vfs.mounts.seq.BeginWrite()
 	vfs.connectLocked(mnt, vd, mntns)
 	vfs.mounts.seq.EndWrite()
-	vd.dentry.mu.Unlock()
+	vdDentry.mu.Unlock()
 	vfs.mountMu.Unlock()
 	return nil
 }