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-rw-r--r--pkg/sentry/fs/fsutil/host_file_mapper.go26
-rw-r--r--pkg/sentry/fs/fsutil/host_mappable.go19
-rw-r--r--pkg/sentry/fs/fsutil/inode_cached.go18
-rw-r--r--pkg/sentry/fs/gofer/file_state.go2
-rw-r--r--pkg/sentry/fs/gofer/fs.go11
-rw-r--r--pkg/sentry/fs/gofer/handles.go12
-rw-r--r--pkg/sentry/fs/gofer/inode.go108
-rw-r--r--pkg/sentry/fs/gofer/session.go5
8 files changed, 184 insertions, 17 deletions
diff --git a/pkg/sentry/fs/fsutil/host_file_mapper.go b/pkg/sentry/fs/fsutil/host_file_mapper.go
index e239f12a5..b06a71cc2 100644
--- a/pkg/sentry/fs/fsutil/host_file_mapper.go
+++ b/pkg/sentry/fs/fsutil/host_file_mapper.go
@@ -209,3 +209,29 @@ func (f *HostFileMapper) unmapAndRemoveLocked(chunkStart uint64, m mapping) {
}
delete(f.mappings, chunkStart)
}
+
+// RegenerateMappings must be called when the file description mapped by f
+// changes, to replace existing mappings of the previous file description.
+func (f *HostFileMapper) RegenerateMappings(fd int) error {
+ f.mapsMu.Lock()
+ defer f.mapsMu.Unlock()
+
+ for chunkStart, m := range f.mappings {
+ prot := syscall.PROT_READ
+ if m.writable {
+ prot |= syscall.PROT_WRITE
+ }
+ _, _, errno := syscall.Syscall6(
+ syscall.SYS_MMAP,
+ m.addr,
+ chunkSize,
+ uintptr(prot),
+ syscall.MAP_SHARED|syscall.MAP_FIXED,
+ uintptr(fd),
+ uintptr(chunkStart))
+ if errno != 0 {
+ return errno
+ }
+ }
+ return nil
+}
diff --git a/pkg/sentry/fs/fsutil/host_mappable.go b/pkg/sentry/fs/fsutil/host_mappable.go
index 693625ddc..30475f340 100644
--- a/pkg/sentry/fs/fsutil/host_mappable.go
+++ b/pkg/sentry/fs/fsutil/host_mappable.go
@@ -100,13 +100,30 @@ func (h *HostMappable) Translate(ctx context.Context, required, optional memmap.
}
// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
-func (h *HostMappable) InvalidateUnsavable(ctx context.Context) error {
+func (h *HostMappable) InvalidateUnsavable(_ context.Context) error {
h.mu.Lock()
h.mappings.InvalidateAll(memmap.InvalidateOpts{})
h.mu.Unlock()
return nil
}
+// NotifyChangeFD must be called after the file description represented by
+// CachedFileObject.FD() changes.
+func (h *HostMappable) NotifyChangeFD() error {
+ // Update existing sentry mappings to refer to the new file description.
+ if err := h.hostFileMapper.RegenerateMappings(h.backingFile.FD()); err != nil {
+ return err
+ }
+
+ // Shoot down existing application mappings of the old file description;
+ // they will be remapped with the new file description on demand.
+ h.mu.Lock()
+ defer h.mu.Unlock()
+
+ h.mappings.InvalidateAll(memmap.InvalidateOpts{})
+ return nil
+}
+
// MapInternal implements platform.File.MapInternal.
func (h *HostMappable) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
return h.hostFileMapper.MapInternal(fr, h.backingFile.FD(), at.Write)
diff --git a/pkg/sentry/fs/fsutil/inode_cached.go b/pkg/sentry/fs/fsutil/inode_cached.go
index dd80757dc..798920d18 100644
--- a/pkg/sentry/fs/fsutil/inode_cached.go
+++ b/pkg/sentry/fs/fsutil/inode_cached.go
@@ -959,6 +959,23 @@ func (c *CachingInodeOperations) InvalidateUnsavable(ctx context.Context) error
return nil
}
+// NotifyChangeFD must be called after the file description represented by
+// CachedFileObject.FD() changes.
+func (c *CachingInodeOperations) NotifyChangeFD() error {
+ // Update existing sentry mappings to refer to the new file description.
+ if err := c.hostFileMapper.RegenerateMappings(c.backingFile.FD()); err != nil {
+ return err
+ }
+
+ // Shoot down existing application mappings of the old file description;
+ // they will be remapped with the new file description on demand.
+ c.mapsMu.Lock()
+ defer c.mapsMu.Unlock()
+
+ c.mappings.InvalidateAll(memmap.InvalidateOpts{})
+ return nil
+}
+
// Evict implements pgalloc.EvictableMemoryUser.Evict.
func (c *CachingInodeOperations) Evict(ctx context.Context, er pgalloc.EvictableRange) {
c.mapsMu.Lock()
@@ -1027,7 +1044,6 @@ func (c *CachingInodeOperations) DecRef(fr platform.FileRange) {
}
c.refs.MergeAdjacent(fr)
c.dataMu.Unlock()
-
}
// MapInternal implements platform.File.MapInternal. This is used when we
diff --git a/pkg/sentry/fs/gofer/file_state.go b/pkg/sentry/fs/gofer/file_state.go
index 9aa68a70e..c2fbb4be9 100644
--- a/pkg/sentry/fs/gofer/file_state.go
+++ b/pkg/sentry/fs/gofer/file_state.go
@@ -29,7 +29,7 @@ func (f *fileOperations) afterLoad() {
// Manually load the open handles.
var err error
// TODO(b/38173783): Context is not plumbed to save/restore.
- f.handles, err = f.inodeOperations.fileState.getHandles(context.Background(), f.flags)
+ f.handles, err = f.inodeOperations.fileState.getHandles(context.Background(), f.flags, f.inodeOperations.cachingInodeOps)
if err != nil {
return fmt.Errorf("failed to re-open handle: %v", err)
}
diff --git a/pkg/sentry/fs/gofer/fs.go b/pkg/sentry/fs/gofer/fs.go
index 8f8ab5d29..cf96dd9fa 100644
--- a/pkg/sentry/fs/gofer/fs.go
+++ b/pkg/sentry/fs/gofer/fs.go
@@ -58,6 +58,11 @@ const (
// If present, sets CachingInodeOperationsOptions.LimitHostFDTranslation to
// true.
limitHostFDTranslationKey = "limit_host_fd_translation"
+
+ // overlayfsStaleRead if present closes cached readonly file after the first
+ // write. This is done to workaround a limitation of overlayfs in kernels
+ // before 4.19 where open FDs are not updated after the file is copied up.
+ overlayfsStaleRead = "overlayfs_stale_read"
)
// defaultAname is the default attach name.
@@ -145,6 +150,7 @@ type opts struct {
version string
privateunixsocket bool
limitHostFDTranslation bool
+ overlayfsStaleRead bool
}
// options parses mount(2) data into structured options.
@@ -247,6 +253,11 @@ func options(data string) (opts, error) {
delete(options, limitHostFDTranslationKey)
}
+ if _, ok := options[overlayfsStaleRead]; ok {
+ o.overlayfsStaleRead = true
+ delete(options, overlayfsStaleRead)
+ }
+
// Fail to attach if the caller wanted us to do something that we
// don't support.
if len(options) > 0 {
diff --git a/pkg/sentry/fs/gofer/handles.go b/pkg/sentry/fs/gofer/handles.go
index 27eeae3d9..39c8ec33d 100644
--- a/pkg/sentry/fs/gofer/handles.go
+++ b/pkg/sentry/fs/gofer/handles.go
@@ -39,14 +39,22 @@ type handles struct {
// Host is an *fd.FD handle. May be nil.
Host *fd.FD
+
+ // isHostBorrowed tells whether 'Host' is owned or borrowed. If owned, it's
+ // closed on destruction, otherwise it's released.
+ isHostBorrowed bool
}
// DecRef drops a reference on handles.
func (h *handles) DecRef() {
h.DecRefWithDestructor(func() {
if h.Host != nil {
- if err := h.Host.Close(); err != nil {
- log.Warningf("error closing host file: %v", err)
+ if h.isHostBorrowed {
+ h.Host.Release()
+ } else {
+ if err := h.Host.Close(); err != nil {
+ log.Warningf("error closing host file: %v", err)
+ }
}
}
// FIXME(b/38173783): Context is not plumbed here.
diff --git a/pkg/sentry/fs/gofer/inode.go b/pkg/sentry/fs/gofer/inode.go
index d918d6620..99910388f 100644
--- a/pkg/sentry/fs/gofer/inode.go
+++ b/pkg/sentry/fs/gofer/inode.go
@@ -100,7 +100,7 @@ type inodeFileState struct {
// true.
//
// Once readHandles becomes non-nil, it can't be changed until
- // inodeFileState.Release(), because of a defect in the
+ // inodeFileState.Release()*, because of a defect in the
// fsutil.CachedFileObject interface: there's no way for the caller of
// fsutil.CachedFileObject.FD() to keep the returned FD open, so if we
// racily replace readHandles after inodeFileState.FD() has returned
@@ -108,6 +108,9 @@ type inodeFileState struct {
// FD. writeHandles can be changed if writeHandlesRW is false, since
// inodeFileState.FD() can't return a write-only FD, but can't be changed
// if writeHandlesRW is true for the same reason.
+ //
+ // * There is one notable exception in recreateReadHandles(), where it dup's
+ // the FD and invalidates the page cache.
readHandles *handles `state:"nosave"`
writeHandles *handles `state:"nosave"`
writeHandlesRW bool `state:"nosave"`
@@ -175,43 +178,124 @@ func (i *inodeFileState) setSharedHandlesLocked(flags fs.FileFlags, h *handles)
// getHandles returns a set of handles for a new file using i opened with the
// given flags.
-func (i *inodeFileState) getHandles(ctx context.Context, flags fs.FileFlags) (*handles, error) {
+func (i *inodeFileState) getHandles(ctx context.Context, flags fs.FileFlags, cache *fsutil.CachingInodeOperations) (*handles, error) {
if !i.canShareHandles() {
return newHandles(ctx, i.file, flags)
}
+
i.handlesMu.Lock()
- defer i.handlesMu.Unlock()
+ h, invalidate, err := i.getHandlesLocked(ctx, flags)
+ i.handlesMu.Unlock()
+
+ if invalidate {
+ cache.NotifyChangeFD()
+ if i.hostMappable != nil {
+ i.hostMappable.NotifyChangeFD()
+ }
+ }
+
+ return h, err
+}
+
+// getHandlesLocked returns a pointer to cached handles and a boolean indicating
+// whether previously open read handle was recreated. Host mappings must be
+// invalidated if so.
+func (i *inodeFileState) getHandlesLocked(ctx context.Context, flags fs.FileFlags) (*handles, bool, error) {
// Do we already have usable shared handles?
if flags.Write {
if i.writeHandles != nil && (i.writeHandlesRW || !flags.Read) {
i.writeHandles.IncRef()
- return i.writeHandles, nil
+ return i.writeHandles, false, nil
}
} else if i.readHandles != nil {
i.readHandles.IncRef()
- return i.readHandles, nil
+ return i.readHandles, false, nil
}
+
// No; get new handles and cache them for future sharing.
h, err := newHandles(ctx, i.file, flags)
if err != nil {
- return nil, err
+ return nil, false, err
+ }
+
+ // Read handles invalidation is needed if:
+ // - Mount option 'overlayfs_stale_read' is set
+ // - Read handle is open: nothing to invalidate otherwise
+ // - Write handle is not open: file was not open for write and is being open
+ // for write now (will trigger copy up in overlayfs).
+ invalidate := false
+ if i.s.overlayfsStaleRead && i.readHandles != nil && i.writeHandles == nil && flags.Write {
+ if err := i.recreateReadHandles(ctx, h, flags); err != nil {
+ return nil, false, err
+ }
+ invalidate = true
}
i.setSharedHandlesLocked(flags, h)
- return h, nil
+ return h, invalidate, nil
+}
+
+func (i *inodeFileState) recreateReadHandles(ctx context.Context, writer *handles, flags fs.FileFlags) error {
+ h := writer
+ if !flags.Read {
+ // Writer can't be used for read, must create a new handle.
+ var err error
+ h, err = newHandles(ctx, i.file, fs.FileFlags{Read: true})
+ if err != nil {
+ return err
+ }
+ defer h.DecRef()
+ }
+
+ if i.readHandles.Host == nil {
+ // If current readHandles doesn't have a host FD, it can simply be replaced.
+ i.readHandles.DecRef()
+
+ h.IncRef()
+ i.readHandles = h
+ return nil
+ }
+
+ if h.Host == nil {
+ // Current read handle has a host FD and can't be replaced with one that
+ // doesn't, because it breaks fsutil.CachedFileObject.FD() contract.
+ log.Warningf("Read handle can't be invalidated, reads may return stale data")
+ return nil
+ }
+
+ // Due to a defect in the fsutil.CachedFileObject interface,
+ // readHandles.Host.FD() may be used outside locks, making it impossible to
+ // reliably close it. To workaround it, we dup the new FD into the old one, so
+ // operations on the old will see the new data. Then, make the new handle take
+ // ownereship of the old FD and mark the old readHandle to not close the FD
+ // when done.
+ if err := syscall.Dup2(h.Host.FD(), i.readHandles.Host.FD()); err != nil {
+ return err
+ }
+
+ h.Host.Close()
+ h.Host = fd.New(i.readHandles.Host.FD())
+ i.readHandles.isHostBorrowed = true
+ i.readHandles.DecRef()
+
+ h.IncRef()
+ i.readHandles = h
+ return nil
}
// ReadToBlocksAt implements fsutil.CachedFileObject.ReadToBlocksAt.
func (i *inodeFileState) ReadToBlocksAt(ctx context.Context, dsts safemem.BlockSeq, offset uint64) (uint64, error) {
i.handlesMu.RLock()
- defer i.handlesMu.RUnlock()
- return i.readHandles.readWriterAt(ctx, int64(offset)).ReadToBlocks(dsts)
+ n, err := i.readHandles.readWriterAt(ctx, int64(offset)).ReadToBlocks(dsts)
+ i.handlesMu.RUnlock()
+ return n, err
}
// WriteFromBlocksAt implements fsutil.CachedFileObject.WriteFromBlocksAt.
func (i *inodeFileState) WriteFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error) {
i.handlesMu.RLock()
- defer i.handlesMu.RUnlock()
- return i.writeHandles.readWriterAt(ctx, int64(offset)).WriteFromBlocks(srcs)
+ n, err := i.writeHandles.readWriterAt(ctx, int64(offset)).WriteFromBlocks(srcs)
+ i.handlesMu.RUnlock()
+ return n, err
}
// SetMaskedAttributes implements fsutil.CachedFileObject.SetMaskedAttributes.
@@ -449,7 +533,7 @@ func (i *inodeOperations) NonBlockingOpen(ctx context.Context, p fs.PermMask) (*
}
func (i *inodeOperations) getFileDefault(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
- h, err := i.fileState.getHandles(ctx, flags)
+ h, err := i.fileState.getHandles(ctx, flags, i.cachingInodeOps)
if err != nil {
return nil, err
}
diff --git a/pkg/sentry/fs/gofer/session.go b/pkg/sentry/fs/gofer/session.go
index 50da865c1..0da608548 100644
--- a/pkg/sentry/fs/gofer/session.go
+++ b/pkg/sentry/fs/gofer/session.go
@@ -122,6 +122,10 @@ type session struct {
// CachingInodeOperations created by the session.
limitHostFDTranslation bool
+ // overlayfsStaleRead when set causes the readonly handle to be invalidated
+ // after file is open for write.
+ overlayfsStaleRead bool
+
// connID is a unique identifier for the session connection.
connID string `state:"wait"`
@@ -257,6 +261,7 @@ func Root(ctx context.Context, dev string, filesystem fs.Filesystem, superBlockF
aname: o.aname,
superBlockFlags: superBlockFlags,
limitHostFDTranslation: o.limitHostFDTranslation,
+ overlayfsStaleRead: o.overlayfsStaleRead,
mounter: mounter,
}
s.EnableLeakCheck("gofer.session")
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-18 18:35:12 +0000