diff options
| author | NeilBrown <neil@brown.name> | 2025-11-13 11:18:35 +1100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-11-14 13:15:58 +0100 |
| commit | 833d2b3a072f7ff6005bf84c065c7cbda81a8aaa (patch) | |
| tree | 4da3dc2db7f97c8c8d4c46672ac533f2cebbc17d /security | |
| parent | ac50950ca143fd637dec4f7457a9162e1a4344e8 (diff) | |
Add start_renaming_two_dentries()
A few callers want to lock for a rename and already have both dentries.
Also debugfs does want to perform a lookup but doesn't want permission
checking, so start_renaming_dentry() cannot be used.
This patch introduces start_renaming_two_dentries() which is given both
dentries. debugfs performs one lookup itself. As it will only continue
with a negative dentry and as those cannot be renamed or unlinked, it is
safe to do the lookup before getting the rename locks.
overlayfs uses start_renaming_two_dentries() in three places and selinux
uses it twice in sel_make_policy_nodes().
In sel_make_policy_nodes() we now lock for rename twice instead of just
once so the combined operation is no longer atomic w.r.t the parent
directory locks. As selinux_state.policy_mutex is held across the whole
operation this does not open up any interesting races.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20251113002050.676694-13-neilb@ownmail.net
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'security')
| -rw-r--r-- | security/selinux/selinuxfs.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c index 232e087bce3e..404e08bf60ba 100644 --- a/security/selinux/selinuxfs.c +++ b/security/selinux/selinuxfs.c @@ -506,6 +506,7 @@ static int sel_make_policy_nodes(struct selinux_fs_info *fsi, { int ret = 0; struct dentry *tmp_parent, *tmp_bool_dir, *tmp_class_dir; + struct renamedata rd = {}; unsigned int bool_num = 0; char **bool_names = NULL; int *bool_values = NULL; @@ -539,9 +540,14 @@ static int sel_make_policy_nodes(struct selinux_fs_info *fsi, if (ret) goto out; - lock_rename(tmp_parent, fsi->sb->s_root); + rd.old_parent = tmp_parent; + rd.new_parent = fsi->sb->s_root; /* booleans */ + ret = start_renaming_two_dentries(&rd, tmp_bool_dir, fsi->bool_dir); + if (ret) + goto out; + d_exchange(tmp_bool_dir, fsi->bool_dir); swap(fsi->bool_num, bool_num); @@ -549,12 +555,17 @@ static int sel_make_policy_nodes(struct selinux_fs_info *fsi, swap(fsi->bool_pending_values, bool_values); fsi->bool_dir = tmp_bool_dir; + end_renaming(&rd); /* classes */ + ret = start_renaming_two_dentries(&rd, tmp_class_dir, fsi->class_dir); + if (ret) + goto out; + d_exchange(tmp_class_dir, fsi->class_dir); fsi->class_dir = tmp_class_dir; - unlock_rename(tmp_parent, fsi->sb->s_root); + end_renaming(&rd); out: sel_remove_old_bool_data(bool_num, bool_names, bool_values); |