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-rw-r--r--pkg/sentry/fsimpl/ext/BUILD1
-rw-r--r--pkg/sentry/fsimpl/ext/filesystem.go8
-rw-r--r--pkg/sentry/fsimpl/memfs/BUILD1
-rw-r--r--pkg/sentry/fsimpl/memfs/filesystem.go8
-rw-r--r--pkg/sentry/vfs/BUILD1
-rw-r--r--pkg/sentry/vfs/filesystem.go54
-rw-r--r--pkg/sentry/vfs/filesystem_impl_util.go26
-rw-r--r--pkg/sentry/vfs/pathname.go153
-rw-r--r--pkg/sentry/vfs/testutil.go9
9 files changed, 260 insertions, 1 deletions
diff --git a/pkg/sentry/fsimpl/ext/BUILD b/pkg/sentry/fsimpl/ext/BUILD
index 7ccff8b0d..880b7bcd3 100644
--- a/pkg/sentry/fsimpl/ext/BUILD
+++ b/pkg/sentry/fsimpl/ext/BUILD
@@ -38,6 +38,7 @@ go_library(
"//pkg/abi/linux",
"//pkg/binary",
"//pkg/fd",
+ "//pkg/fspath",
"//pkg/log",
"//pkg/sentry/arch",
"//pkg/sentry/context",
diff --git a/pkg/sentry/fsimpl/ext/filesystem.go b/pkg/sentry/fsimpl/ext/filesystem.go
index 2d15e8aaf..e7aa3b41b 100644
--- a/pkg/sentry/fsimpl/ext/filesystem.go
+++ b/pkg/sentry/fsimpl/ext/filesystem.go
@@ -20,6 +20,7 @@ import (
"sync"
"gvisor.dev/gvisor/pkg/abi/linux"
+ "gvisor.dev/gvisor/pkg/fspath"
"gvisor.dev/gvisor/pkg/sentry/context"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/ext/disklayout"
"gvisor.dev/gvisor/pkg/sentry/vfs"
@@ -441,3 +442,10 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
return syserror.EROFS
}
+
+// PrependPath implements vfs.FilesystemImpl.PrependPath.
+func (fs *filesystem) PrependPath(ctx context.Context, vfsroot, vd vfs.VirtualDentry, b *fspath.Builder) error {
+ fs.mu.RLock()
+ defer fs.mu.RUnlock()
+ return vfs.GenericPrependPath(vfsroot, vd, b)
+}
diff --git a/pkg/sentry/fsimpl/memfs/BUILD b/pkg/sentry/fsimpl/memfs/BUILD
index bc5c0b591..0cc751eb8 100644
--- a/pkg/sentry/fsimpl/memfs/BUILD
+++ b/pkg/sentry/fsimpl/memfs/BUILD
@@ -32,6 +32,7 @@ go_library(
deps = [
"//pkg/abi/linux",
"//pkg/amutex",
+ "//pkg/fspath",
"//pkg/sentry/arch",
"//pkg/sentry/context",
"//pkg/sentry/kernel/auth",
diff --git a/pkg/sentry/fsimpl/memfs/filesystem.go b/pkg/sentry/fsimpl/memfs/filesystem.go
index 08a9cb8ef..1f2a5122a 100644
--- a/pkg/sentry/fsimpl/memfs/filesystem.go
+++ b/pkg/sentry/fsimpl/memfs/filesystem.go
@@ -19,6 +19,7 @@ import (
"sync/atomic"
"gvisor.dev/gvisor/pkg/abi/linux"
+ "gvisor.dev/gvisor/pkg/fspath"
"gvisor.dev/gvisor/pkg/sentry/context"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
@@ -582,3 +583,10 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
inode.decLinksLocked()
return nil
}
+
+// PrependPath implements vfs.FilesystemImpl.PrependPath.
+func (fs *filesystem) PrependPath(ctx context.Context, vfsroot, vd vfs.VirtualDentry, b *fspath.Builder) error {
+ fs.mu.RLock()
+ defer fs.mu.RUnlock()
+ return vfs.GenericPrependPath(vfsroot, vd, b)
+}
diff --git a/pkg/sentry/vfs/BUILD b/pkg/sentry/vfs/BUILD
index 59237c3b9..e3e554b88 100644
--- a/pkg/sentry/vfs/BUILD
+++ b/pkg/sentry/vfs/BUILD
@@ -17,6 +17,7 @@ go_library(
"mount.go",
"mount_unsafe.go",
"options.go",
+ "pathname.go",
"permissions.go",
"resolving_path.go",
"testutil.go",
diff --git a/pkg/sentry/vfs/filesystem.go b/pkg/sentry/vfs/filesystem.go
index dfbd2372a..8011eba3f 100644
--- a/pkg/sentry/vfs/filesystem.go
+++ b/pkg/sentry/vfs/filesystem.go
@@ -18,6 +18,7 @@ import (
"sync/atomic"
"gvisor.dev/gvisor/pkg/abi/linux"
+ "gvisor.dev/gvisor/pkg/fspath"
"gvisor.dev/gvisor/pkg/sentry/context"
)
@@ -185,5 +186,56 @@ type FilesystemImpl interface {
// UnlinkAt removes the non-directory file at rp.
UnlinkAt(ctx context.Context, rp *ResolvingPath) error
- // TODO: d_path(); extended attributes; inotify_add_watch(); bind()
+ // PrependPath prepends a path from vd to vd.Mount().Root() to b.
+ //
+ // If vfsroot.Ok(), it is the contextual VFS root; if it is encountered
+ // before vd.Mount().Root(), PrependPath should stop prepending path
+ // components and return a PrependPathAtVFSRootError.
+ //
+ // If traversal of vd.Dentry()'s ancestors encounters an independent
+ // ("root") Dentry that is not vd.Mount().Root() (i.e. vd.Dentry() is not a
+ // descendant of vd.Mount().Root()), PrependPath should stop prepending
+ // path components and return a PrependPathAtNonMountRootError.
+ //
+ // Filesystems for which Dentries do not have meaningful paths may prepend
+ // an arbitrary descriptive string to b and then return a
+ // PrependPathSyntheticError.
+ //
+ // Most implementations can acquire the appropriate locks to ensure that
+ // Dentry.Name() and Dentry.Parent() are fixed for vd.Dentry() and all of
+ // its ancestors, then call GenericPrependPath.
+ //
+ // Preconditions: vd.Mount().Filesystem().Impl() == this FilesystemImpl.
+ PrependPath(ctx context.Context, vfsroot, vd VirtualDentry, b *fspath.Builder) error
+
+ // TODO: extended attributes; inotify_add_watch(); bind()
+}
+
+// PrependPathAtVFSRootError is returned by implementations of
+// FilesystemImpl.PrependPath() when they encounter the contextual VFS root.
+type PrependPathAtVFSRootError struct{}
+
+// Error implements error.Error.
+func (PrependPathAtVFSRootError) Error() string {
+ return "vfs.FilesystemImpl.PrependPath() reached VFS root"
+}
+
+// PrependPathAtNonMountRootError is returned by implementations of
+// FilesystemImpl.PrependPath() when they encounter an independent ancestor
+// Dentry that is not the Mount root.
+type PrependPathAtNonMountRootError struct{}
+
+// Error implements error.Error.
+func (PrependPathAtNonMountRootError) Error() string {
+ return "vfs.FilesystemImpl.PrependPath() reached root other than Mount root"
+}
+
+// PrependPathSyntheticError is returned by implementations of
+// FilesystemImpl.PrependPath() for which prepended names do not represent real
+// paths.
+type PrependPathSyntheticError struct{}
+
+// Error implements error.Error.
+func (PrependPathSyntheticError) Error() string {
+ return "vfs.FilesystemImpl.PrependPath() prepended synthetic name"
}
diff --git a/pkg/sentry/vfs/filesystem_impl_util.go b/pkg/sentry/vfs/filesystem_impl_util.go
index 465e610e0..7315a588e 100644
--- a/pkg/sentry/vfs/filesystem_impl_util.go
+++ b/pkg/sentry/vfs/filesystem_impl_util.go
@@ -16,6 +16,8 @@ package vfs
import (
"strings"
+
+ "gvisor.dev/gvisor/pkg/fspath"
)
// GenericParseMountOptions parses a comma-separated list of options of the
@@ -41,3 +43,27 @@ func GenericParseMountOptions(str string) map[string]string {
}
return m
}
+
+// GenericPrependPath may be used by implementations of
+// FilesystemImpl.PrependPath() for which a single statically-determined lock
+// or set of locks is sufficient to ensure its preconditions (as opposed to
+// e.g. per-Dentry locks).
+//
+// Preconditions: Dentry.Name() and Dentry.Parent() must be held constant for
+// vd.Dentry() and all of its ancestors.
+func GenericPrependPath(vfsroot, vd VirtualDentry, b *fspath.Builder) error {
+ mnt, d := vd.mount, vd.dentry
+ for {
+ if mnt == vfsroot.mount && d == vfsroot.dentry {
+ return PrependPathAtVFSRootError{}
+ }
+ if d == mnt.root {
+ return nil
+ }
+ if d.parent == nil {
+ return PrependPathAtNonMountRootError{}
+ }
+ b.PrependComponent(d.name)
+ d = d.parent
+ }
+}
diff --git a/pkg/sentry/vfs/pathname.go b/pkg/sentry/vfs/pathname.go
new file mode 100644
index 000000000..8e155654f
--- /dev/null
+++ b/pkg/sentry/vfs/pathname.go
@@ -0,0 +1,153 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs
+
+import (
+ "sync"
+
+ "gvisor.dev/gvisor/pkg/fspath"
+ "gvisor.dev/gvisor/pkg/sentry/context"
+ "gvisor.dev/gvisor/pkg/syserror"
+)
+
+var fspathBuilderPool = sync.Pool{
+ New: func() interface{} {
+ return &fspath.Builder{}
+ },
+}
+
+func getFSPathBuilder() *fspath.Builder {
+ return fspathBuilderPool.Get().(*fspath.Builder)
+}
+
+func putFSPathBuilder(b *fspath.Builder) {
+ // No methods can be called on b after b.String(), so reset it to its zero
+ // value (as returned by fspathBuilderPool.New) instead.
+ *b = fspath.Builder{}
+ fspathBuilderPool.Put(b)
+}
+
+// PathnameWithDeleted returns an absolute pathname to vd, consistent with
+// Linux's d_path(). In particular, if vd.Dentry() has been disowned,
+// PathnameWithDeleted appends " (deleted)" to the returned pathname.
+func (vfs *VirtualFilesystem) PathnameWithDeleted(ctx context.Context, vfsroot, vd VirtualDentry) (string, error) {
+ b := getFSPathBuilder()
+ defer putFSPathBuilder(b)
+ haveRef := false
+ defer func() {
+ if haveRef {
+ vd.DecRef()
+ }
+ }()
+
+ origD := vd.dentry
+loop:
+ for {
+ err := vd.mount.fs.impl.PrependPath(ctx, vfsroot, vd, b)
+ switch err.(type) {
+ case nil:
+ if vd.mount == vfsroot.mount && vd.mount.root == vfsroot.dentry {
+ // GenericPrependPath() will have returned
+ // PrependPathAtVFSRootError in this case since it checks
+ // against vfsroot before mnt.root, but other implementations
+ // of FilesystemImpl.PrependPath() may return nil instead.
+ break loop
+ }
+ nextVD := vfs.getMountpointAt(vd.mount, vfsroot)
+ if !nextVD.Ok() {
+ break loop
+ }
+ if haveRef {
+ vd.DecRef()
+ }
+ vd = nextVD
+ haveRef = true
+ // continue loop
+ case PrependPathSyntheticError:
+ // Skip prepending "/" and appending " (deleted)".
+ return b.String(), nil
+ case PrependPathAtVFSRootError, PrependPathAtNonMountRootError:
+ break loop
+ default:
+ return "", err
+ }
+ }
+ b.PrependByte('/')
+ if origD.IsDisowned() {
+ b.AppendString(" (deleted)")
+ }
+ return b.String(), nil
+}
+
+// PathnameForGetcwd returns an absolute pathname to vd, consistent with
+// Linux's sys_getcwd().
+func (vfs *VirtualFilesystem) PathnameForGetcwd(ctx context.Context, vfsroot, vd VirtualDentry) (string, error) {
+ if vd.dentry.IsDisowned() {
+ return "", syserror.ENOENT
+ }
+
+ b := getFSPathBuilder()
+ defer putFSPathBuilder(b)
+ haveRef := false
+ defer func() {
+ if haveRef {
+ vd.DecRef()
+ }
+ }()
+ unreachable := false
+loop:
+ for {
+ err := vd.mount.fs.impl.PrependPath(ctx, vfsroot, vd, b)
+ switch err.(type) {
+ case nil:
+ if vd.mount == vfsroot.mount && vd.mount.root == vfsroot.dentry {
+ break loop
+ }
+ nextVD := vfs.getMountpointAt(vd.mount, vfsroot)
+ if !nextVD.Ok() {
+ unreachable = true
+ break loop
+ }
+ if haveRef {
+ vd.DecRef()
+ }
+ vd = nextVD
+ haveRef = true
+ case PrependPathAtVFSRootError:
+ break loop
+ case PrependPathAtNonMountRootError, PrependPathSyntheticError:
+ unreachable = true
+ break loop
+ default:
+ return "", err
+ }
+ }
+ b.PrependByte('/')
+ if unreachable {
+ b.PrependString("(unreachable)")
+ }
+ return b.String(), nil
+}
+
+// As of this writing, we do not have equivalents to:
+//
+// - d_absolute_path(), which returns EINVAL if (effectively) any call to
+// FilesystemImpl.PrependPath() would return PrependPathAtNonMountRootError.
+//
+// - dentry_path(), which does not walk up mounts (and only returns the path
+// relative to Filesystem root), but also appends "//deleted" for disowned
+// Dentries.
+//
+// These should be added as necessary.
diff --git a/pkg/sentry/vfs/testutil.go b/pkg/sentry/vfs/testutil.go
index 593144cb7..7a1d9e383 100644
--- a/pkg/sentry/vfs/testutil.go
+++ b/pkg/sentry/vfs/testutil.go
@@ -15,7 +15,10 @@
package vfs
import (
+ "fmt"
+
"gvisor.dev/gvisor/pkg/abi/linux"
+ "gvisor.dev/gvisor/pkg/fspath"
"gvisor.dev/gvisor/pkg/sentry/context"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/syserror"
@@ -114,6 +117,12 @@ func (fs *FDTestFilesystem) UnlinkAt(ctx context.Context, rp *ResolvingPath) err
return syserror.EPERM
}
+// PrependPath implements FilesystemImpl.PrependPath.
+func (fs *FDTestFilesystem) PrependPath(ctx context.Context, vfsroot, vd VirtualDentry, b *fspath.Builder) error {
+ b.PrependComponent(fmt.Sprintf("vfs.fdTestDentry:%p", vd.dentry.impl.(*fdTestDentry)))
+ return PrependPathSyntheticError{}
+}
+
type fdTestDentry struct {
vfsd Dentry
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-02 18:29:39 +0000