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kernfs/cgroupfs: Fix rename.

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Rename was broken for serveral reasons:

- The underlying kernfs.OrderedChildren.Rename had a bug so it could
  never successfully extract OrderedChildren from the dst Inode.

- kernfs.OrderedChildren.Rename didn't check for name collisions on
  the dst.

cgroupfs is the first kernfs-based filesystem to implement rename, so
these code paths weren't exercised.

PiperOrigin-RevId: 444964501
This commit is contained in:
Rahat Mahmood
2022-04-27 14:20:25 -07:00
committed by gVisor bot
parent 5afe17a15d
commit 2ba23ca96c
2 changed files with 93 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+34 -24
View File
@@ -400,6 +400,16 @@ type OrderedChildrenOptions struct {
Writable bool
}
// inodeWithOrderedChildren allows extraction of an OrderedChildren from an
// Inode implementation. A concrete type that both implements the Inode
// interface and embeds OrderedChildren will be castable to this interface, and
// we can get to the embedded OrderedChildren through the orderedChildren
// method.
type inodeWithOrderedChildren interface {
Inode
orderedChildren() *OrderedChildren
}
// OrderedChildren partially implements the Inode interface. OrderedChildren can
// be embedded in directory inodes to keep track of children in the
// directory, and can then be used to implement a generic directory FD -- see
@@ -427,6 +437,11 @@ type OrderedChildren struct {
set map[string]*slot
}
// orderedChildren implements inodeWithOrderedChildren.orderedChildren.
func (o *OrderedChildren) orderedChildren() *OrderedChildren {
return o
}
// Init initializes an OrderedChildren.
func (o *OrderedChildren) Init(opts OrderedChildrenOptions) {
o.writable = opts.Writable
@@ -572,27 +587,6 @@ func (o *OrderedChildren) removeLocked(name string) {
}
}
// Precondition: caller must hold o.mu for writing.
func (o *OrderedChildren) replaceChildLocked(ctx context.Context, name string, newI Inode) {
if s, ok := o.set[name]; ok {
if s.static {
panic(fmt.Sprintf("replacing a static inode: %v", s.inode))
}
// Existing slot with given name, simply replace the dentry.
s.inode = newI
}
// No existing slot with given name, create and hash new slot.
s := &slot{
name: name,
inode: newI,
static: false,
}
o.order.PushBack(s)
o.set[name] = s
}
// Precondition: caller must hold o.mu for reading or writing.
func (o *OrderedChildren) checkExistingLocked(name string, child Inode) error {
s, ok := o.set[name]
@@ -640,11 +634,11 @@ func (o *OrderedChildren) Rename(ctx context.Context, oldname, newname string, c
if !o.writable {
return linuxerr.EPERM
}
dst, ok := dstDir.(interface{}).(*OrderedChildren)
dstIOC, ok := dstDir.(inodeWithOrderedChildren)
if !ok {
return linuxerr.EXDEV
}
dst := dstIOC.orderedChildren()
if !dst.writable {
return linuxerr.EPERM
}
@@ -659,12 +653,28 @@ func (o *OrderedChildren) Rename(ctx context.Context, oldname, newname string, c
dst.mu.Lock()
defer dst.mu.Unlock()
}
// Ensure target inode exists in src.
if err := o.checkExistingLocked(oldname, child); err != nil {
return err
}
// Ensure no name collision in dst.
if _, ok := dst.set[newname]; ok {
return linuxerr.EEXIST
}
// Remove from src.
o.removeLocked(oldname)
dst.replaceChildLocked(ctx, newname, child)
// Add to dst.
s := &slot{
name: newname,
inode: child,
}
dst.order.PushBack(s)
dst.set[newname] = s
return nil
}
test/syscalls/linux/cgroup.cc
+59
View File
@@ -490,6 +490,65 @@ TEST(Cgroup, MkdirWithPermissions) {
EXPECT_TRUE(S_ISDIR(s2.st_mode));
}
TEST(Cgroup, CantRenameControlFile) {
SKIP_IF(!CgroupsAvailable());
Mounter m(ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir()));
Cgroup c = ASSERT_NO_ERRNO_AND_VALUE(m.MountCgroupfs(""));
const std::string control_file_path = c.Relpath("cgroup.procs");
EXPECT_THAT(
rename(c.Relpath("cgroup.procs").c_str(), c.Relpath("foo").c_str()),
SyscallFailsWithErrno(ENOTDIR));
}
TEST(Cgroup, CrossDirRenameNotAllowed) {
SKIP_IF(!CgroupsAvailable());
Mounter m(ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir()));
Cgroup c = ASSERT_NO_ERRNO_AND_VALUE(m.MountCgroupfs(""));
Cgroup dir1 = ASSERT_NO_ERRNO_AND_VALUE(c.CreateChild("dir1"));
Cgroup dir2 = ASSERT_NO_ERRNO_AND_VALUE(c.CreateChild("dir2"));
Cgroup target = ASSERT_NO_ERRNO_AND_VALUE(dir1.CreateChild("target"));
// Move to sibling directory.
EXPECT_THAT(rename(target.Path().c_str(), dir2.Relpath("target").c_str()),
SyscallFailsWithErrno(EIO));
// Move to parent directory.
EXPECT_THAT(rename(target.Path().c_str(), c.Relpath("target").c_str()),
SyscallFailsWithErrno(EIO));
// Original directory unaffected.
EXPECT_THAT(Exists(target.Path()), IsPosixErrorOkAndHolds(true));
}
TEST(Cgroup, RenameNameCollision) {
SKIP_IF(!CgroupsAvailable());
Mounter m(ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir()));
Cgroup c = ASSERT_NO_ERRNO_AND_VALUE(m.MountCgroupfs(""));
Cgroup dir1 = ASSERT_NO_ERRNO_AND_VALUE(c.CreateChild("dir1"));
Cgroup dir2 = ASSERT_NO_ERRNO_AND_VALUE(c.CreateChild("dir2"));
// Collision with dir.
EXPECT_THAT(rename(dir1.Path().c_str(), dir2.Path().c_str()),
SyscallFailsWithErrno(EEXIST));
// Collision with control file.
EXPECT_THAT(rename(dir1.Path().c_str(), c.Relpath("cgroup.procs").c_str()),
SyscallFailsWithErrno(EEXIST));
}
TEST(Cgroup, Rename) {
SKIP_IF(!CgroupsAvailable());
Mounter m(ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir()));
Cgroup c = ASSERT_NO_ERRNO_AND_VALUE(m.MountCgroupfs(""));
Cgroup child = ASSERT_NO_ERRNO_AND_VALUE(c.CreateChild("child"));
Cgroup target = ASSERT_NO_ERRNO_AND_VALUE(child.CreateChild("oldname"));
ASSERT_THAT(rename(target.Path().c_str(), child.Relpath("newname").c_str()),
SyscallSucceeds());
EXPECT_THAT(Exists(child.Relpath("newname")), IsPosixErrorOkAndHolds(true));
EXPECT_THAT(Exists(child.Relpath("oldname")), IsPosixErrorOkAndHolds(false));
}
TEST(MemoryCgroup, MemoryUsageInBytes) {
SKIP_IF(!CgroupsAvailable());