[PATCH 31/39] convert selinuxfs

Al Viro
2025-09-20T07:48:09Z

Tree has invariant part + two subtrees that get replaced upon each
policy load. Invariant parts stay for the lifetime of filesystem,
these two subdirs - from policy load to policy load (serialized
on lock_rename(root, ...)).

All object creations are via d_alloc_name()+d_add() inside selinuxfs,
all removals are via simple_recursive_removal().

Turn those d_add() into d_make_persistent()+dput() and that's mostly it.
Don't bother to store the dentry of /policy_capabilities - it belongs
to invariant part of tree and we only use it to populate that directory,
so there's no reason to keep it around afterwards.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
security/selinux/selinuxfs.c | 52 +++++++++++++++++++++---------------
1 file changed, 30 insertions(+), 22 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 9aa1d03ab612..dc1bb49664f2 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -75,7 +75,6 @@ struct selinux_fs_info {
struct dentry *class_dir;
unsigned long last_class_ino;
bool policy_opened;
- struct dentry *policycap_dir;
unsigned long last_ino;
struct super_block *sb;
};
@@ -1404,7 +1403,8 @@ static int sel_make_bools(struct selinux_policy *newpolicy, struct dentry *bool_
isec->initialized = LABEL_INITIALIZED;
inode->i_fop = &sel_bool_ops;
inode->i_ino = i|SEL_BOOL_INO_OFFSET;
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);
}
out:
free_page((unsigned long)page);
@@ -1614,7 +1614,8 @@ static int sel_make_avc_files(struct dentry *dir)

inode->i_fop = files[i].ops;
inode->i_ino = ++fsi->last_ino;
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);
}

return 0;
@@ -1645,7 +1646,8 @@ static int sel_make_ss_files(struct dentry *dir)

inode->i_fop = files[i].ops;
inode->i_ino = ++fsi->last_ino;
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);
}

return 0;
@@ -1696,7 +1698,8 @@ static int sel_make_initcon_files(struct dentry *dir)

inode->i_fop = &sel_initcon_ops;
inode->i_ino = i|SEL_INITCON_INO_OFFSET;
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);
}

return 0;
@@ -1800,7 +1803,8 @@ static int sel_make_perm_files(struct selinux_policy *newpolicy,
inode->i_fop = &sel_perm_ops;
/* i+1 since perm values are 1-indexed */
inode->i_ino = sel_perm_to_ino(classvalue, i + 1);
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);
}
rc = 0;
out:
@@ -1831,7 +1835,8 @@ static int sel_make_class_dir_entries(struct selinux_policy *newpolicy,

inode->i_fop = &sel_class_ops;
inode->i_ino = sel_class_to_ino(index);
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);

dentry = sel_make_dir(dir, "perms", &fsi->last_class_ino);
if (IS_ERR(dentry))
@@ -1879,7 +1884,7 @@ static int sel_make_classes(struct selinux_policy *newpolicy,
return rc;
}

-static int sel_make_policycap(struct selinux_fs_info *fsi)
+static int sel_make_policycap(struct selinux_fs_info *fsi, struct dentry *dir)
{
unsigned int iter;
struct dentry *dentry = NULL;
@@ -1887,10 +1892,10 @@ static int sel_make_policycap(struct selinux_fs_info *fsi)

for (iter = 0; iter <= POLICYDB_CAP_MAX; iter++) {
if (iter < ARRAY_SIZE(selinux_policycap_names))
- dentry = d_alloc_name(fsi->policycap_dir,
+ dentry = d_alloc_name(dir,
selinux_policycap_names[iter]);
else
- dentry = d_alloc_name(fsi->policycap_dir, "unknown");
+ dentry = d_alloc_name(dir, "unknown");

if (dentry == NULL)
return -ENOMEM;
@@ -1903,7 +1908,8 @@ static int sel_make_policycap(struct selinux_fs_info *fsi)

inode->i_fop = &sel_policycap_ops;
inode->i_ino = iter | SEL_POLICYCAP_INO_OFFSET;
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);
}

return 0;
@@ -1929,11 +1935,12 @@ static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
inode->i_ino = ++(*ino);
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
/* bump link count on parent directory, too */
inc_nlink(d_inode(dir));

- return dentry;
+ dput(dentry);
+ return dentry; // borrowed
}

static int reject_all(struct mnt_idmap *idmap, struct inode *inode, int mask)
@@ -1966,10 +1973,11 @@ static struct dentry *sel_make_swapover_dir(struct super_block *sb,
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
inode_lock(sb->s_root->d_inode);
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
inc_nlink(sb->s_root->d_inode);
inode_unlock(sb->s_root->d_inode);
- return dentry;
+ dput(dentry);
+ return dentry; // borrowed
}

#define NULL_FILE_NAME "null"
@@ -2040,7 +2048,8 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
isec->initialized = LABEL_INITIALIZED;

init_special_inode(inode, S_IFCHR | S_IRUGO | S_IWUGO, MKDEV(MEM_MAJOR, 3));
- d_add(dentry, inode);
+ d_make_persistent(dentry, inode);
+ dput(dentry);

dentry = sel_make_dir(sb->s_root, "avc", &fsi->last_ino);
if (IS_ERR(dentry)) {
@@ -2079,15 +2088,14 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
goto err;
}

- fsi->policycap_dir = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
+ dentry = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
&fsi->last_ino);
- if (IS_ERR(fsi->policycap_dir)) {
- ret = PTR_ERR(fsi->policycap_dir);
- fsi->policycap_dir = NULL;
+ if (IS_ERR(dentry)) {
+ ret = PTR_ERR(dentry);
goto err;
}

- ret = sel_make_policycap(fsi);
+ ret = sel_make_policycap(fsi, dentry);
if (ret) {
pr_err("SELinux: failed to load policy capabilities\n");
goto err;
@@ -2119,7 +2127,7 @@ static int sel_init_fs_context(struct fs_context *fc)
static void sel_kill_sb(struct super_block *sb)
{
selinux_fs_info_free(sb);
- kill_litter_super(sb);
+ kill_anon_super(sb);
}

static struct file_system_type sel_fs_type = {
--
2.47.3