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kernel: expose umount list to ioctl interface (#2950)

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This idea is borrowed from simonpunk's susfs4ksu.
What we see here is that, yeah well, lets just have userspace send us
what it
wants unmounted, this is better than hardcoding everything.

This also solves that issue where MNT_DETACH fails, as long as we send
unmountables in proper order.

A small anti-duplicate mechanism is also added.

While in-kernel umount is a bit worse than zygisk-provider-based ones,
this can still
serve as a healthy alternative.

---------

- Remove duplicate checks

Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>
Co-authored-by: weishu <twsxtd@gmail.com>
Co-authored-by: ShirkNeko <109797057+ShirkNeko@users.noreply.github.com>
This commit is contained in:
backslashxx
2025-11-18 11:10:44 +08:00
committed by ShirkNeko
parent 58c8289890
commit 029ae8d389
48 changed files with 252 additions and 260 deletions
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36
kernel/kernel_umount.c
View File

@@ -43,24 +43,6 @@ static const struct ksu_feature_handler kernel_umount_handler = {
.set_handler = kernel_umount_feature_set,
};
static bool should_umount(struct path *path)
{
if (!path) {
return false;
}
if (current->nsproxy->mnt_ns == init_nsproxy.mnt_ns) {
pr_info("ignore global mnt namespace process: %d\n", current_uid().val);
return false;
}
if (path->mnt && path->mnt->mnt_sb && path->mnt->mnt_sb->s_type) {
const char *fstype = path->mnt->mnt_sb->s_type->name;
return strcmp(fstype, "overlay") == 0;
}
return false;
}
extern int path_umount(struct path *path, int flags);
static void ksu_umount_mnt(struct path *path, int flags)
@@ -71,7 +53,7 @@ static void ksu_umount_mnt(struct path *path, int flags)
}
}
void try_umount(const char *mnt, bool check_mnt, int flags)
void try_umount(const char *mnt, int flags)
{
struct path path;
int err = kern_path(mnt, 0, &path);
@@ -85,12 +67,6 @@ void try_umount(const char *mnt, bool check_mnt, int flags)
return;
}
// we are only interest in some specific mounts
if (check_mnt && !should_umount(&path)) {
path_put(&path);
return;
}
ksu_umount_mnt(&path, flags);
}
@@ -107,8 +83,14 @@ static void umount_tw_func(struct callback_head *cb)
saved = override_creds(tw->old_cred);
}
// fixme: use `collect_mounts` and `iterate_mount` to iterate all mountpoint and
// filter the mountpoint whose target is `/data/adb`
struct mount_entry *entry;
down_read(&mount_list_lock);
list_for_each_entry(entry, &mount_list, list) {
pr_info("%s: unmounting: %s flags 0x%x\n", __func__, entry->umountable, entry->flags);
try_umount(entry->umountable, entry->flags);
}
up_read(&mount_list_lock);
ksu_umount_manager_execute_all(tw->old_cred);
if (saved)