@@ -2931,6 +2931,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
struct mount *old;
struct mount *parent;
struct mountpoint *mp, *old_mp;
+ struct path ns_root;
int err;
bool attached;
@@ -2985,6 +2986,14 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
if (p == old)
goto out;
+ ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
+ ns_root.dentry = ns_root.mnt->mnt_root;
+ path_get(&ns_root);
+ /* See argument in pivot_root() */
+ if (path_equal(new_path, &ns_root))
+ usermodehelper_disable();
+
+
err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp,
attached);
if (err)
@@ -2996,6 +3005,9 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
if (attached)
put_mountpoint(old_mp);
out:
+ if (path_equal(new_path, &ns_root))
+ usermodehelper_enable();
+
unlock_mount(mp);
if (!err) {
if (attached)
@@ -3997,6 +4009,8 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
goto out2;
get_fs_root(current->fs, &root);
+ /* UMHs started from old root should finish before we switch root under */
+ usermodehelper_disable(); // XXX error handling
old_mp = lock_mount(&old);
error = PTR_ERR(old_mp);
if (IS_ERR(old_mp))
@@ -4058,6 +4072,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
error = 0;
out4:
unlock_mount(old_mp);
+ usermodehelper_enable();
if (!error)
mntput_no_expire(ex_parent);
out3:
We want to make sure no UMHs started with an old root survive into the world with the new root (they may fail when it is not expected). Therefore, insert a wait for existing UMHs termination (this assumes UMH runtime is finite). A motivation are asynchronous module loads that start in initrd and they may be (un)intentionally terminated by a userspace cleanup during rootfs transition. This is also inspired by an ancient problem [1]. This is just a rough idea, only superficially tested, no broader context (VFS locking et al) is considered. [1] https://kernelnewbies.org/KernelProjects/usermode-helper-enhancements#Filesystem_suspend Signed-off-by: Michal Koutný <mkoutny@suse.com> --- I'm not amused by this patch. I'm sending it to get some NAck reasons (besides indefinite UMH lifetime) and get it off my head. Thanks. fs/namespace.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)