kernel: Implementing editable, removable mount points
This commit is contained in:
ShirkNeko
314
kernel/umount_manager.c
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314
kernel/umount_manager.c
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@@ -0,0 +1,314 @@
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#include "umount_manager.h"
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/uaccess.h>
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#include <linux/namei.h>
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#include <linux/path.h>
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#include <linux/mount.h>
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#include <linux/cred.h>
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#include "klog.h"
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static struct umount_manager g_umount_mgr = {
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.entry_count = 0,
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.max_entries = 64,
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};
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extern int path_umount(struct path *path, int flags);
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static bool check_path_busy(const char *path)
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{
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struct path kpath;
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int err;
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err = kern_path(path, 0, &kpath);
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if (err) {
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return false;
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}
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bool busy = (kpath.mnt->mnt_root != kpath.dentry);
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path_put(&kpath);
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return busy;
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}
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static struct umount_entry *find_entry_locked(const char *path)
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{
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struct umount_entry *entry;
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list_for_each_entry(entry, &g_umount_mgr.entry_list, list) {
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if (strcmp(entry->path, path) == 0) {
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return entry;
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}
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}
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return NULL;
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}
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static int init_default_entries(void)
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{
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int ret;
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const struct {
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const char *path;
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bool check_mnt;
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int flags;
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} defaults[] = {
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{ "/odm", true, 0 },
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{ "/system", true, 0 },
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{ "/vendor", true, 0 },
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{ "/product", true, 0 },
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{ "/system_ext", true, 0 },
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{ "/data/adb/modules", false, MNT_DETACH },
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};
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for (int i = 0; i < ARRAY_SIZE(defaults); i++) {
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ret = ksu_umount_manager_add(defaults[i].path,
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defaults[i].check_mnt,
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defaults[i].flags,
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true); // is_default = true
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if (ret) {
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pr_err("Failed to add default entry: %s, ret=%d\n",
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defaults[i].path, ret);
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return ret;
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}
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}
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pr_info("Initialized %zu default umount entries\n", ARRAY_SIZE(defaults));
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return 0;
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}
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int ksu_umount_manager_init(void)
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{
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INIT_LIST_HEAD(&g_umount_mgr.entry_list);
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spin_lock_init(&g_umount_mgr.lock);
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return init_default_entries();
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}
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void ksu_umount_manager_exit(void)
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{
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struct umount_entry *entry, *tmp;
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unsigned long flags;
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spin_lock_irqsave(&g_umount_mgr.lock, flags);
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list_for_each_entry_safe(entry, tmp, &g_umount_mgr.entry_list, list) {
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list_del(&entry->list);
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kfree(entry);
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g_umount_mgr.entry_count--;
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}
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spin_unlock_irqrestore(&g_umount_mgr.lock, flags);
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pr_info("Umount manager cleaned up\n");
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}
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int ksu_umount_manager_add(const char *path, bool check_mnt, int flags, bool is_default)
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{
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struct umount_entry *entry;
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unsigned long irqflags;
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int ret = 0;
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if (!path || strlen(path) == 0 || strlen(path) >= 256) {
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return -EINVAL;
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}
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spin_lock_irqsave(&g_umount_mgr.lock, irqflags);
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if (g_umount_mgr.entry_count >= g_umount_mgr.max_entries) {
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pr_err("Umount manager: max entries reached\n");
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ret = -ENOMEM;
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goto out;
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}
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if (find_entry_locked(path)) {
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pr_warn("Umount manager: path already exists: %s\n", path);
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ret = -EEXIST;
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goto out;
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}
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entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
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if (!entry) {
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ret = -ENOMEM;
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goto out;
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}
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strncpy(entry->path, path, sizeof(entry->path) - 1);
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entry->check_mnt = check_mnt;
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entry->flags = flags;
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entry->state = UMOUNT_STATE_IDLE;
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entry->is_default = is_default;
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entry->ref_count = 0;
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list_add_tail(&entry->list, &g_umount_mgr.entry_list);
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g_umount_mgr.entry_count++;
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pr_info("Umount manager: added %s entry: %s\n",
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is_default ? "default" : "custom", path);
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out:
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spin_unlock_irqrestore(&g_umount_mgr.lock, irqflags);
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return ret;
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}
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int ksu_umount_manager_remove(const char *path)
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{
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struct umount_entry *entry;
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unsigned long flags;
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int ret = 0;
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if (!path) {
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return -EINVAL;
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}
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spin_lock_irqsave(&g_umount_mgr.lock, flags);
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entry = find_entry_locked(path);
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if (!entry) {
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ret = -ENOENT;
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goto out;
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}
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if (entry->is_default) {
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pr_err("Umount manager: cannot remove default entry: %s\n", path);
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ret = -EPERM;
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goto out;
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}
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if (entry->state == UMOUNT_STATE_BUSY || entry->ref_count > 0) {
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pr_err("Umount manager: entry is busy: %s\n", path);
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ret = -EBUSY;
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goto out;
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}
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list_del(&entry->list);
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g_umount_mgr.entry_count--;
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kfree(entry);
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pr_info("Umount manager: removed entry: %s\n", path);
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out:
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spin_unlock_irqrestore(&g_umount_mgr.lock, flags);
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return ret;
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}
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bool ksu_umount_path_is_busy(const char *path)
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{
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return check_path_busy(path);
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}
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static void execute_umount_entry(struct umount_entry *entry, const struct cred *cred)
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{
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struct path kpath;
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int err;
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entry->ref_count++;
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entry->state = UMOUNT_STATE_ACTIVE;
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err = kern_path(entry->path, 0, &kpath);
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if (err) {
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goto done;
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}
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if (kpath.dentry != kpath.mnt->mnt_root) {
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path_put(&kpath);
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goto done;
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}
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if (entry->check_mnt) {
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if (kpath.mnt && kpath.mnt->mnt_sb && kpath.mnt->mnt_sb->s_type) {
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const char *fstype = kpath.mnt->mnt_sb->s_type->name;
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if (strcmp(fstype, "overlay") != 0) {
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path_put(&kpath);
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goto done;
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}
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}
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}
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err = path_umount(&kpath, entry->flags);
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if (err) {
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pr_info("umount %s failed: %d\n", entry->path, err);
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}
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path_put(&kpath);
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done:
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entry->state = UMOUNT_STATE_IDLE;
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entry->ref_count--;
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}
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void ksu_umount_manager_execute_all(const struct cred *cred)
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{
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struct umount_entry *entry;
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unsigned long flags;
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spin_lock_irqsave(&g_umount_mgr.lock, flags);
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list_for_each_entry(entry, &g_umount_mgr.entry_list, list) {
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if (entry->state == UMOUNT_STATE_IDLE) {
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execute_umount_entry(entry, cred);
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}
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}
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spin_unlock_irqrestore(&g_umount_mgr.lock, flags);
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}
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int ksu_umount_manager_get_entries(struct ksu_umount_entry_info __user *entries, u32 *count)
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{
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struct umount_entry *entry;
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struct ksu_umount_entry_info info;
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unsigned long flags;
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u32 idx = 0;
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u32 max_count = *count;
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spin_lock_irqsave(&g_umount_mgr.lock, flags);
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list_for_each_entry(entry, &g_umount_mgr.entry_list, list) {
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if (idx >= max_count) {
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break;
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}
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memset(&info, 0, sizeof(info));
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strncpy(info.path, entry->path, sizeof(info.path) - 1);
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info.check_mnt = entry->check_mnt;
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info.flags = entry->flags;
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info.is_default = entry->is_default;
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info.state = entry->state;
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info.ref_count = entry->ref_count;
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if (copy_to_user(&entries[idx], &info, sizeof(info))) {
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spin_unlock_irqrestore(&g_umount_mgr.lock, flags);
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return -EFAULT;
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}
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idx++;
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}
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*count = idx;
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spin_unlock_irqrestore(&g_umount_mgr.lock, flags);
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return 0;
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}
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int ksu_umount_manager_clear_custom(void)
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{
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struct umount_entry *entry, *tmp;
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unsigned long flags;
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u32 cleared = 0;
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spin_lock_irqsave(&g_umount_mgr.lock, flags);
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list_for_each_entry_safe(entry, tmp, &g_umount_mgr.entry_list, list) {
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if (!entry->is_default && entry->state == UMOUNT_STATE_IDLE && entry->ref_count == 0) {
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list_del(&entry->list);
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kfree(entry);
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g_umount_mgr.entry_count--;
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cleared++;
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}
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}
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spin_unlock_irqrestore(&g_umount_mgr.lock, flags);
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pr_info("Umount manager: cleared %u custom entries\n", cleared);
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return 0;
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}
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