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Diffstat (limited to 'pkg/sentry/vfs/mount.go')
-rw-r--r--pkg/sentry/vfs/mount.go125
1 files changed, 81 insertions, 44 deletions
diff --git a/pkg/sentry/vfs/mount.go b/pkg/sentry/vfs/mount.go
index d1d29d0cd..9da09d4c1 100644
--- a/pkg/sentry/vfs/mount.go
+++ b/pkg/sentry/vfs/mount.go
@@ -114,7 +114,7 @@ func (mnt *Mount) Options() MountOptions {
defer mnt.vfs.mountMu.Unlock()
return MountOptions{
Flags: mnt.Flags,
- ReadOnly: mnt.readOnly(),
+ ReadOnly: mnt.ReadOnly(),
}
}
@@ -126,16 +126,14 @@ func (mnt *Mount) Options() MountOptions {
//
// +stateify savable
type MountNamespace struct {
+ MountNamespaceRefs
+
// Owner is the usernamespace that owns this mount namespace.
Owner *auth.UserNamespace
// root is the MountNamespace's root mount. root is immutable.
root *Mount
- // refs is the reference count. refs is accessed using atomic memory
- // operations.
- refs int64
-
// mountpoints maps all Dentries which are mount points in this namespace
// to the number of Mounts for which they are mount points. mountpoints is
// protected by VirtualFilesystem.mountMu.
@@ -154,22 +152,22 @@ type MountNamespace struct {
// NewMountNamespace returns a new mount namespace with a root filesystem
// configured by the given arguments. A reference is taken on the returned
// MountNamespace.
-func (vfs *VirtualFilesystem) NewMountNamespace(ctx context.Context, creds *auth.Credentials, source, fsTypeName string, opts *GetFilesystemOptions) (*MountNamespace, error) {
+func (vfs *VirtualFilesystem) NewMountNamespace(ctx context.Context, creds *auth.Credentials, source, fsTypeName string, opts *MountOptions) (*MountNamespace, error) {
rft := vfs.getFilesystemType(fsTypeName)
if rft == nil {
ctx.Warningf("Unknown filesystem type: %s", fsTypeName)
return nil, syserror.ENODEV
}
- fs, root, err := rft.fsType.GetFilesystem(ctx, vfs, creds, source, *opts)
+ fs, root, err := rft.fsType.GetFilesystem(ctx, vfs, creds, source, opts.GetFilesystemOptions)
if err != nil {
return nil, err
}
mntns := &MountNamespace{
Owner: creds.UserNamespace,
- refs: 1,
mountpoints: make(map[*Dentry]uint32),
}
- mntns.root = newMount(vfs, fs, root, mntns, &MountOptions{})
+ mntns.EnableLeakCheck()
+ mntns.root = newMount(vfs, fs, root, mntns, opts)
return mntns, nil
}
@@ -263,16 +261,20 @@ func (vfs *VirtualFilesystem) ConnectMountAt(ctx context.Context, creds *auth.Cr
}
// MountAt creates and mounts a Filesystem configured by the given arguments.
-func (vfs *VirtualFilesystem) MountAt(ctx context.Context, creds *auth.Credentials, source string, target *PathOperation, fsTypeName string, opts *MountOptions) error {
+// The VirtualFilesystem will hold a reference to the Mount until it is unmounted.
+//
+// This method returns the mounted Mount without a reference, for convenience
+// during VFS setup when there is no chance of racing with unmount.
+func (vfs *VirtualFilesystem) MountAt(ctx context.Context, creds *auth.Credentials, source string, target *PathOperation, fsTypeName string, opts *MountOptions) (*Mount, error) {
mnt, err := vfs.MountDisconnected(ctx, creds, source, fsTypeName, opts)
if err != nil {
- return err
+ return nil, err
}
defer mnt.DecRef(ctx)
if err := vfs.ConnectMountAt(ctx, creds, mnt, target); err != nil {
- return err
+ return nil, err
}
- return nil
+ return mnt, nil
}
// UmountAt removes the Mount at the given path.
@@ -369,8 +371,9 @@ type umountRecursiveOptions struct {
//
// umountRecursiveLocked is analogous to Linux's fs/namespace.c:umount_tree().
//
-// Preconditions: vfs.mountMu must be locked. vfs.mounts.seq must be in a
-// writer critical section.
+// Preconditions:
+// * vfs.mountMu must be locked.
+// * vfs.mounts.seq must be in a writer critical section.
func (vfs *VirtualFilesystem) umountRecursiveLocked(mnt *Mount, opts *umountRecursiveOptions, vdsToDecRef []VirtualDentry, mountsToDecRef []*Mount) ([]VirtualDentry, []*Mount) {
if !mnt.umounted {
mnt.umounted = true
@@ -399,9 +402,11 @@ func (vfs *VirtualFilesystem) umountRecursiveLocked(mnt *Mount, opts *umountRecu
// connectLocked makes vd the mount parent/point for mnt. It consumes
// references held by vd.
//
-// Preconditions: vfs.mountMu must be locked. vfs.mounts.seq must be in a
-// writer critical section. d.mu must be locked. mnt.parent() == nil, i.e. mnt
-// must not already be connected.
+// Preconditions:
+// * vfs.mountMu must be locked.
+// * vfs.mounts.seq must be in a writer critical section.
+// * d.mu must be locked.
+// * mnt.parent() == nil, i.e. mnt must not already be connected.
func (vfs *VirtualFilesystem) connectLocked(mnt *Mount, vd VirtualDentry, mntns *MountNamespace) {
if checkInvariants {
if mnt.parent() != nil {
@@ -429,8 +434,10 @@ func (vfs *VirtualFilesystem) connectLocked(mnt *Mount, vd VirtualDentry, mntns
// disconnectLocked makes vd have no mount parent/point and returns its old
// mount parent/point with a reference held.
//
-// Preconditions: vfs.mountMu must be locked. vfs.mounts.seq must be in a
-// writer critical section. mnt.parent() != nil.
+// Preconditions:
+// * vfs.mountMu must be locked.
+// * vfs.mounts.seq must be in a writer critical section.
+// * mnt.parent() != nil.
func (vfs *VirtualFilesystem) disconnectLocked(mnt *Mount) VirtualDentry {
vd := mnt.loadKey()
if checkInvariants {
@@ -498,17 +505,10 @@ func (mnt *Mount) DecRef(ctx context.Context) {
}
}
-// IncRef increments mntns' reference count.
-func (mntns *MountNamespace) IncRef() {
- if atomic.AddInt64(&mntns.refs, 1) <= 1 {
- panic("MountNamespace.IncRef() called without holding a reference")
- }
-}
-
// DecRef decrements mntns' reference count.
func (mntns *MountNamespace) DecRef(ctx context.Context) {
vfs := mntns.root.fs.VirtualFilesystem()
- if refs := atomic.AddInt64(&mntns.refs, -1); refs == 0 {
+ mntns.MountNamespaceRefs.DecRef(func() {
vfs.mountMu.Lock()
vfs.mounts.seq.BeginWrite()
vdsToDecRef, mountsToDecRef := vfs.umountRecursiveLocked(mntns.root, &umountRecursiveOptions{
@@ -522,9 +522,7 @@ func (mntns *MountNamespace) DecRef(ctx context.Context) {
for _, mnt := range mountsToDecRef {
mnt.DecRef(ctx)
}
- } else if refs < 0 {
- panic("MountNamespace.DecRef() called without holding a reference")
- }
+ })
}
// getMountAt returns the last Mount in the stack mounted at (mnt, d). It takes
@@ -576,8 +574,9 @@ retryFirst:
// mnt. It takes a reference on the returned VirtualDentry. If no such mount
// point exists (i.e. mnt is a root mount), getMountpointAt returns (nil, nil).
//
-// Preconditions: References are held on mnt and root. vfsroot is not (mnt,
-// mnt.root).
+// Preconditions:
+// * References are held on mnt and root.
+// * vfsroot is not (mnt, mnt.root).
func (vfs *VirtualFilesystem) getMountpointAt(ctx context.Context, mnt *Mount, vfsroot VirtualDentry) VirtualDentry {
// The first mount is special-cased:
//
@@ -651,6 +650,13 @@ retryFirst:
return VirtualDentry{mnt, d}
}
+// SetMountReadOnly sets the mount as ReadOnly.
+func (vfs *VirtualFilesystem) SetMountReadOnly(mnt *Mount, ro bool) error {
+ vfs.mountMu.Lock()
+ defer vfs.mountMu.Unlock()
+ return mnt.setReadOnlyLocked(ro)
+}
+
// CheckBeginWrite increments the counter of in-progress write operations on
// mnt. If mnt is mounted MS_RDONLY, CheckBeginWrite does nothing and returns
// EROFS.
@@ -688,7 +694,8 @@ func (mnt *Mount) setReadOnlyLocked(ro bool) error {
return nil
}
-func (mnt *Mount) readOnly() bool {
+// ReadOnly returns true if mount is readonly.
+func (mnt *Mount) ReadOnly() bool {
return atomic.LoadInt64(&mnt.writers) < 0
}
@@ -731,11 +738,23 @@ func (mntns *MountNamespace) Root() VirtualDentry {
//
// Preconditions: taskRootDir.Ok().
func (vfs *VirtualFilesystem) GenerateProcMounts(ctx context.Context, taskRootDir VirtualDentry, buf *bytes.Buffer) {
- vfs.mountMu.Lock()
- defer vfs.mountMu.Unlock()
rootMnt := taskRootDir.mount
+
+ vfs.mountMu.Lock()
mounts := rootMnt.submountsLocked()
+ // Take a reference on mounts since we need to drop vfs.mountMu before
+ // calling vfs.PathnameReachable() (=> FilesystemImpl.PrependPath()).
+ for _, mnt := range mounts {
+ mnt.IncRef()
+ }
+ vfs.mountMu.Unlock()
+ defer func() {
+ for _, mnt := range mounts {
+ mnt.DecRef(ctx)
+ }
+ }()
sort.Slice(mounts, func(i, j int) bool { return mounts[i].ID < mounts[j].ID })
+
for _, mnt := range mounts {
// Get the path to this mount relative to task root.
mntRootVD := VirtualDentry{
@@ -746,7 +765,7 @@ func (vfs *VirtualFilesystem) GenerateProcMounts(ctx context.Context, taskRootDi
if err != nil {
// For some reason we didn't get a path. Log a warning
// and run with empty path.
- ctx.Warningf("Error getting pathname for mount root %+v: %v", mnt.root, err)
+ ctx.Warningf("VFS.GenerateProcMounts: error getting pathname for mount root %+v: %v", mnt.root, err)
path = ""
}
if path == "" {
@@ -756,7 +775,7 @@ func (vfs *VirtualFilesystem) GenerateProcMounts(ctx context.Context, taskRootDi
}
opts := "rw"
- if mnt.readOnly() {
+ if mnt.ReadOnly() {
opts = "ro"
}
if mnt.Flags.NoATime {
@@ -780,11 +799,25 @@ func (vfs *VirtualFilesystem) GenerateProcMounts(ctx context.Context, taskRootDi
//
// Preconditions: taskRootDir.Ok().
func (vfs *VirtualFilesystem) GenerateProcMountInfo(ctx context.Context, taskRootDir VirtualDentry, buf *bytes.Buffer) {
- vfs.mountMu.Lock()
- defer vfs.mountMu.Unlock()
rootMnt := taskRootDir.mount
+
+ vfs.mountMu.Lock()
mounts := rootMnt.submountsLocked()
+ // Take a reference on mounts since we need to drop vfs.mountMu before
+ // calling vfs.PathnameReachable() (=> FilesystemImpl.PrependPath()) or
+ // vfs.StatAt() (=> FilesystemImpl.StatAt()).
+ for _, mnt := range mounts {
+ mnt.IncRef()
+ }
+ vfs.mountMu.Unlock()
+ defer func() {
+ for _, mnt := range mounts {
+ mnt.DecRef(ctx)
+ }
+ }()
sort.Slice(mounts, func(i, j int) bool { return mounts[i].ID < mounts[j].ID })
+
+ creds := auth.CredentialsFromContext(ctx)
for _, mnt := range mounts {
// Get the path to this mount relative to task root.
mntRootVD := VirtualDentry{
@@ -795,7 +828,7 @@ func (vfs *VirtualFilesystem) GenerateProcMountInfo(ctx context.Context, taskRoo
if err != nil {
// For some reason we didn't get a path. Log a warning
// and run with empty path.
- ctx.Warningf("Error getting pathname for mount root %+v: %v", mnt.root, err)
+ ctx.Warningf("VFS.GenerateProcMountInfo: error getting pathname for mount root %+v: %v", mnt.root, err)
path = ""
}
if path == "" {
@@ -808,9 +841,10 @@ func (vfs *VirtualFilesystem) GenerateProcMountInfo(ctx context.Context, taskRoo
Root: mntRootVD,
Start: mntRootVD,
}
- statx, err := vfs.StatAt(ctx, auth.NewAnonymousCredentials(), pop, &StatOptions{})
+ statx, err := vfs.StatAt(ctx, creds, pop, &StatOptions{})
if err != nil {
// Well that's not good. Ignore this mount.
+ ctx.Warningf("VFS.GenerateProcMountInfo: failed to stat mount root %+v: %v", mnt.root, err)
break
}
@@ -822,6 +856,9 @@ func (vfs *VirtualFilesystem) GenerateProcMountInfo(ctx context.Context, taskRoo
fmt.Fprintf(buf, "%d ", mnt.ID)
// (2) Parent ID (or this ID if there is no parent).
+ // Note that even if the call to mnt.parent() races with Mount
+ // destruction (which is possible since we're not holding vfs.mountMu),
+ // its Mount.ID will still be valid.
pID := mnt.ID
if p := mnt.parent(); p != nil {
pID = p.ID
@@ -844,7 +881,7 @@ func (vfs *VirtualFilesystem) GenerateProcMountInfo(ctx context.Context, taskRoo
// (6) Mount options.
opts := "rw"
- if mnt.readOnly() {
+ if mnt.ReadOnly() {
opts = "ro"
}
if mnt.Flags.NoATime {
@@ -883,7 +920,7 @@ func superBlockOpts(mountPath string, mnt *Mount) string {
// gVisor doesn't (yet) have a concept of super block options, so we
// use the ro/rw bit from the mount flag.
opts := "rw"
- if mnt.readOnly() {
+ if mnt.ReadOnly() {
opts = "ro"
}
generated by cgit v1.2.3 (git 2.39.1) at 2025-04-03 04:43:33 +0000