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-rw-r--r--pkg/sentry/fs/dirent.go75
-rw-r--r--pkg/sentry/syscalls/linux/sys_file.go43
2 files changed, 75 insertions, 43 deletions
diff --git a/pkg/sentry/fs/dirent.go b/pkg/sentry/fs/dirent.go
index 7191c5c30..a42c03e98 100644
--- a/pkg/sentry/fs/dirent.go
+++ b/pkg/sentry/fs/dirent.go
@@ -1027,11 +1027,14 @@ func (d *Dirent) flush() {
}
}
-// Busy indicates whether this Dirent is a mount point or root dirent.
-func (d *Dirent) Busy() bool {
+// isMountPoint returns true if the dirent is a mount point or the root.
+func (d *Dirent) isMountPoint() bool {
d.mu.Lock()
defer d.mu.Unlock()
+ return d.isMountPointLocked()
+}
+func (d *Dirent) isMountPointLocked() bool {
return d.mounted || d.parent == nil
}
@@ -1137,7 +1140,7 @@ func (d *Dirent) Remove(ctx context.Context, root *Dirent, name string) error {
}
// Remove cannot remove a mount point.
- if child.Busy() {
+ if child.isMountPoint() {
return syscall.EBUSY
}
@@ -1211,7 +1214,7 @@ func (d *Dirent) RemoveDirectory(ctx context.Context, root *Dirent, name string)
}
// Remove cannot remove a mount point.
- if child.Busy() {
+ if child.isMountPoint() {
return syscall.EBUSY
}
@@ -1457,12 +1460,20 @@ func MayDelete(ctx context.Context, root, dir *Dirent, name string) error {
return mayDelete(ctx, dir, victim)
}
-func mayDelete(ctx context.Context, dir *Dirent, victim *Dirent) error {
+func mayDelete(ctx context.Context, dir, victim *Dirent) error {
if err := dir.Inode.CheckPermission(ctx, PermMask{Write: true, Execute: true}); err != nil {
return err
}
- return checkSticky(ctx, dir, victim)
+ if err := checkSticky(ctx, dir, victim); err != nil {
+ return err
+ }
+
+ if victim.IsRoot() {
+ return syserror.EBUSY
+ }
+
+ return nil
}
// Rename atomically converts the child of oldParent named oldName to a
@@ -1491,33 +1502,28 @@ func Rename(ctx context.Context, root *Dirent, oldParent *Dirent, oldName string
return syscall.ENOENT
}
- // Check constraints on the object being renamed.
+ // renamed is the dirent that will be renamed to something else.
renamed, err := oldParent.walk(ctx, root, oldName, false /* may unlock */)
if err != nil {
return err
}
defer renamed.DecRef()
- // Make sure we have write permissions on old and new parent.
+ // Check that the renamed dirent is deletable.
if err := mayDelete(ctx, oldParent, renamed); err != nil {
return err
}
- if newParent != oldParent {
- if err := newParent.Inode.CheckPermission(ctx, PermMask{Write: true, Execute: true}); err != nil {
- return err
- }
+
+ // Check that the renamed dirent is not a mount point.
+ if renamed.isMountPointLocked() {
+ return syscall.EBUSY
}
// Source should not be an ancestor of the target.
- if renamed == newParent {
+ if newParent.descendantOf(renamed) {
return syscall.EINVAL
}
- // Is the thing we're trying to rename busy?
- if renamed.Busy() {
- return syscall.EBUSY
- }
-
// Per rename(2): "... EACCES: ... or oldpath is a directory and does not
// allow write permission (needed to update the .. entry)."
if IsDir(renamed.Inode.StableAttr) {
@@ -1526,21 +1532,42 @@ func Rename(ctx context.Context, root *Dirent, oldParent *Dirent, oldName string
}
}
- // Check constraints on the object being replaced, if any.
+ // replaced is the dirent that is being overwritten by rename.
replaced, err := newParent.walk(ctx, root, newName, false /* may unlock */)
- if err == nil {
+ if err != nil {
+ if err != syserror.ENOENT {
+ return err
+ }
+
+ // Make sure we can create a new child in the new parent.
+ if err := newParent.Inode.CheckPermission(ctx, PermMask{Write: true, Execute: true}); err != nil {
+ return err
+ }
+ } else {
+ // Check constraints on the dirent being replaced.
+
// NOTE: We don't want to keep replaced alive
// across the Rename, so must call DecRef manually (no defer).
+ // Check that we can delete replaced.
+ if err := mayDelete(ctx, oldParent, renamed); err != nil {
+ replaced.DecRef()
+ return err
+ }
+
// Target should not be an ancestor of source.
- if replaced == oldParent {
+ if oldParent.descendantOf(replaced) {
replaced.DecRef()
- // Why is this not EINVAL? See fs/namei.c.
+
+ // Note that Linux returns EINVAL if the source is an
+ // ancestor of target, but ENOTEMPTY if the target is
+ // an ancestor of source (unless RENAME_EXCHANGE flag
+ // is present). See fs/namei.c:renameat2.
return syscall.ENOTEMPTY
}
- // Is the thing we're trying to replace busy?
- if replaced.Busy() {
+ // Check that replaced is not a mount point.
+ if replaced.isMountPointLocked() {
replaced.DecRef()
return syscall.EBUSY
}
diff --git a/pkg/sentry/syscalls/linux/sys_file.go b/pkg/sentry/syscalls/linux/sys_file.go
index 015afda9b..64704bb88 100644
--- a/pkg/sentry/syscalls/linux/sys_file.go
+++ b/pkg/sentry/syscalls/linux/sys_file.go
@@ -1042,11 +1042,9 @@ func rmdirAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr) error {
return err
}
- // Special case: rmdir rejects anything with '.' as last component.
- // This would be handled by the busy check for the current working
- // directory, but this is how it's done.
- if (len(path) == 1 && path == ".") || (len(path) > 1 && path[len(path)-2:] == "/.") {
- return syserror.EINVAL
+ // Special case: removing the root always returns EBUSY.
+ if path == "/" {
+ return syserror.EBUSY
}
return fileOpAt(t, dirFD, path, func(root *fs.Dirent, d *fs.Dirent, name string) error {
@@ -1054,6 +1052,15 @@ func rmdirAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr) error {
return syserror.ENOTDIR
}
+ // Linux returns different ernos when the path ends in single
+ // dot vs. double dots.
+ switch name {
+ case ".":
+ return syserror.EINVAL
+ case "..":
+ return syserror.ENOTEMPTY
+ }
+
if err := fs.MayDelete(t, root, d, name); err != nil {
return err
}
@@ -1829,27 +1836,25 @@ func renameAt(t *kernel.Task, oldDirFD kdefs.FD, oldAddr usermem.Addr, newDirFD
return syserror.ENOTDIR
}
- // Root cannot be renamed to anything.
- //
- // TODO: This catches the case when the rename
- // argument is exactly "/", but we should return EBUSY when
- // renaming any mount point, or when the argument is not
- // exactly "/" but still resolves to the root, like "/.." or
- // "/bin/..".
- if oldParent == root && oldName == "." {
- return syscall.EBUSY
+ // Rename rejects paths that end in ".", "..", or empty (i.e.
+ // the root) with EBUSY.
+ switch oldName {
+ case "", ".", "..":
+ return syserror.EBUSY
}
+
return fileOpAt(t, newDirFD, newPath, func(root *fs.Dirent, newParent *fs.Dirent, newName string) error {
if !fs.IsDir(newParent.Inode.StableAttr) {
return syserror.ENOTDIR
}
- // Nothing can be renamed to root.
- //
- // TODO: Same as above.
- if newParent == root && newName == "." {
- return syscall.EBUSY
+ // Rename rejects paths that end in ".", "..", or empty
+ // (i.e. the root) with EBUSY.
+ switch newName {
+ case "", ".", "..":
+ return syserror.EBUSY
}
+
return fs.Rename(t, root, oldParent, oldName, newParent, newName)
})
})
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-26 11:28:50 +0000