On policy reload selinuxfs replaces two subdirectories (/booleans
and /class) with new variants. Unfortunately, that's done with
serious abuses of directory locking.
1) lock_rename() should be done to parents, not to objects being
exchanged
2) there's a bunch of reasons why it should not be done for directories
that do not have a common ancestor; most of those do not apply to
selinuxfs, but even in the best case the proof is subtle and brittle.
3) failure halfway through the creation of /class will leak
names and values arrays.
4) use of d_genocide() is also rather brittle; it's probably not much of
a bug per se, but e.g. an overmount of /sys/fs/selinuxfs/classes/shm/index
with any regular file will end up with leaked mount on policy reload.
Sure, don't do it, but...
Let's stop messing with disconnected directories; just create
a temporary (/.swapover) with no permissions for anyone (on the
level of ->permission() returing -EPERM, no matter who's calling
it) and build the new /booleans and /class in there; then
lock_rename on root and that temporary directory and d_exchange()
old and new both for class and booleans. Then unlock and use
simple_recursive_removal() to take the temporary out; it's much
more robust.
And instead of bothering with separate pathways for freeing
new (on failure halfway through) and old (on success) names/values,
do all freeing in one place. With temporaries swapped with the
old ones when we are past all possible failures.
The only user-visible difference is that /.swapover shows up
(but isn't possible to open, look up into, etc.) for the
duration of policy reload.
Reviewed-by: Stephen Smalley <stephen.smalley.work@xxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
[PM: applied some fixes from Al post merge]
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
---
security/selinux/selinuxfs.c | 144 ++++++++++++++++-------------------
1 file changed, 66 insertions(+), 78 deletions(-)
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 6c596ae7fef9..0619a1cbbfbe 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -336,12 +336,9 @@ static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
unsigned long *ino);
/* declaration for sel_make_policy_nodes */
-static struct dentry *sel_make_disconnected_dir(struct super_block *sb,
+static struct dentry *sel_make_swapover_dir(struct super_block *sb,
unsigned long *ino);
-/* declaration for sel_make_policy_nodes */
-static void sel_remove_entries(struct dentry *de);
-
static ssize_t sel_read_mls(struct file *filp, char __user *buf,
size_t count, loff_t *ppos)
{
@@ -508,13 +505,13 @@ static int sel_make_policy_nodes(struct selinux_fs_info *fsi,
struct selinux_policy *newpolicy)
{
int ret = 0;
- struct dentry *tmp_parent, *tmp_bool_dir, *tmp_class_dir, *old_dentry;
- unsigned int tmp_bool_num, old_bool_num;
- char **tmp_bool_names, **old_bool_names;
- int *tmp_bool_values, *old_bool_values;
+ struct dentry *tmp_parent, *tmp_bool_dir, *tmp_class_dir;
+ unsigned int bool_num = 0;
+ char **bool_names = NULL;
+ int *bool_values = NULL;
unsigned long tmp_ino = fsi->last_ino; /* Don't increment last_ino in this function */
- tmp_parent = sel_make_disconnected_dir(fsi->sb, &tmp_ino);
+ tmp_parent = sel_make_swapover_dir(fsi->sb, &tmp_ino);
if (IS_ERR(tmp_parent))
return PTR_ERR(tmp_parent);
@@ -532,8 +529,8 @@ static int sel_make_policy_nodes(struct selinux_fs_info *fsi,
goto out;
}
- ret = sel_make_bools(newpolicy, tmp_bool_dir, &tmp_bool_num,
- &tmp_bool_names, &tmp_bool_values);
+ ret = sel_make_bools(newpolicy, tmp_bool_dir, &bool_num,
+ &bool_names, &bool_values);
if (ret)
goto out;
@@ -542,38 +539,30 @@ static int sel_make_policy_nodes(struct selinux_fs_info *fsi,
if (ret)
goto out;
+ lock_rename(tmp_parent, fsi->sb->s_root);
+
/* booleans */
- old_dentry = fsi->bool_dir;
- lock_rename(tmp_bool_dir, old_dentry);
d_exchange(tmp_bool_dir, fsi->bool_dir);
- old_bool_num = fsi->bool_num;
- old_bool_names = fsi->bool_pending_names;
- old_bool_values = fsi->bool_pending_values;
-
- fsi->bool_num = tmp_bool_num;
- fsi->bool_pending_names = tmp_bool_names;
- fsi->bool_pending_values = tmp_bool_values;
-
- sel_remove_old_bool_data(old_bool_num, old_bool_names, old_bool_values);
+ swap(fsi->bool_num, bool_num);
+ swap(fsi->bool_pending_names, bool_names);
+ swap(fsi->bool_pending_values, bool_values);
fsi->bool_dir = tmp_bool_dir;
- unlock_rename(tmp_bool_dir, old_dentry);
/* classes */
- old_dentry = fsi->class_dir;
- lock_rename(tmp_class_dir, old_dentry);
d_exchange(tmp_class_dir, fsi->class_dir);
fsi->class_dir = tmp_class_dir;
- unlock_rename(tmp_class_dir, old_dentry);
+
+ unlock_rename(tmp_parent, fsi->sb->s_root);
out:
+ sel_remove_old_bool_data(bool_num, bool_names, bool_values);
/* Since the other temporary dirs are children of tmp_parent
* this will handle all the cleanup in the case of a failure before
* the swapover
*/
- sel_remove_entries(tmp_parent);
- dput(tmp_parent); /* d_genocide() only handles the children */
+ simple_recursive_removal(tmp_parent, NULL);
return ret;
}
@@ -1351,54 +1340,48 @@ static const struct file_operations sel_commit_bools_ops = {
.llseek = generic_file_llseek,
};
-static void sel_remove_entries(struct dentry *de)
-{
- d_genocide(de);
- shrink_dcache_parent(de);
-}
-
static int sel_make_bools(struct selinux_policy *newpolicy, struct dentry *bool_dir,
unsigned int *bool_num, char ***bool_pending_names,
int **bool_pending_values)
{
int ret;
- ssize_t len;
- struct dentry *dentry = NULL;
- struct inode *inode = NULL;
- struct inode_security_struct *isec;
- char **names = NULL, *page;
+ char **names, *page;
u32 i, num;
- int *values = NULL;
- u32 sid;
- ret = -ENOMEM;
page = (char *)get_zeroed_page(GFP_KERNEL);
if (!page)
- goto out;
+ return -ENOMEM;
- ret = security_get_bools(newpolicy, &num, &names, &values);
+ ret = security_get_bools(newpolicy, &num, &names, bool_pending_values);
if (ret)
goto out;
+ *bool_num = num;
+ *bool_pending_names = names;
+
for (i = 0; i < num; i++) {
- ret = -ENOMEM;
+ struct dentry *dentry;
+ struct inode *inode;
+ struct inode_security_struct *isec;
+ ssize_t len;
+ u32 sid;
+
+ len = snprintf(page, PAGE_SIZE, "/%s/%s", BOOL_DIR_NAME, names[i]);
+ if (len >= PAGE_SIZE) {
+ ret = -ENAMETOOLONG;
+ break;
+ }
dentry = d_alloc_name(bool_dir, names[i]);
- if (!dentry)
- goto out;
+ if (!dentry) {
+ ret = -ENOMEM;
+ break;
+ }
- ret = -ENOMEM;
inode = sel_make_inode(bool_dir->d_sb, S_IFREG | S_IRUGO | S_IWUSR);
if (!inode) {
dput(dentry);
- goto out;
- }
-
- ret = -ENAMETOOLONG;
- len = snprintf(page, PAGE_SIZE, "/%s/%s", BOOL_DIR_NAME, names[i]);
- if (len >= PAGE_SIZE) {
- dput(dentry);
- iput(inode);
- goto out;
+ ret = -ENOMEM;
+ break;
}
isec = selinux_inode(inode);
@@ -1416,23 +1399,8 @@ static int sel_make_bools(struct selinux_policy *newpolicy, struct dentry *bool_
inode->i_ino = i|SEL_BOOL_INO_OFFSET;
d_add(dentry, inode);
}
- *bool_num = num;
- *bool_pending_names = names;
- *bool_pending_values = values;
-
- free_page((unsigned long)page);
- return 0;
out:
free_page((unsigned long)page);
-
- if (names) {
- for (i = 0; i < num; i++)
- kfree(names[i]);
- kfree(names);
- }
- kfree(values);
- sel_remove_entries(bool_dir);
-
return ret;
}
@@ -1961,20 +1929,40 @@ static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
return dentry;
}
-static struct dentry *sel_make_disconnected_dir(struct super_block *sb,
+static int reject_all(struct mnt_idmap *idmap, struct inode *inode, int mask)
+{
+ return -EPERM; // no access for anyone, root or no root.
+}
+
+static const struct inode_operations swapover_dir_inode_operations = {
+ .lookup = simple_lookup,
+ .permission = reject_all,
+};
+
+static struct dentry *sel_make_swapover_dir(struct super_block *sb,
unsigned long *ino)
{
- struct inode *inode = sel_make_inode(sb, S_IFDIR | S_IRUGO | S_IXUGO);
+ struct dentry *dentry = d_alloc_name(sb->s_root, ".swapover");
+ struct inode *inode;
- if (!inode)
+ if (!dentry)
return ERR_PTR(-ENOMEM);
- inode->i_op = &simple_dir_inode_operations;
- inode->i_fop = &simple_dir_operations;
+ inode = sel_make_inode(sb, S_IFDIR);
+ if (!inode) {
+ dput(dentry);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ inode->i_op = &swapover_dir_inode_operations;
inode->i_ino = ++(*ino);
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
- return d_obtain_alias(inode);
+ inode_lock(sb->s_root->d_inode);
+ d_add(dentry, inode);
+ inc_nlink(sb->s_root->d_inode);
+ inode_unlock(sb->s_root->d_inode);
+ return dentry;
}
#define NULL_FILE_NAME "null"
--
2.39.2
