diff options
| -rw-r--r-- | kernel/fork.c | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 7f0ab5ee948..6eb9362775f 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1323,3 +1323,235 @@ void __init proc_caches_init(void) sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); } + + +/* + * Check constraints on flags passed to the unshare system call and + * force unsharing of additional process context as appropriate. + */ +static inline void check_unshare_flags(unsigned long *flags_ptr) +{ + /* + * If unsharing a thread from a thread group, must also + * unshare vm. + */ + if (*flags_ptr & CLONE_THREAD) + *flags_ptr |= CLONE_VM; + + /* + * If unsharing vm, must also unshare signal handlers. + */ + if (*flags_ptr & CLONE_VM) + *flags_ptr |= CLONE_SIGHAND; + + /* + * If unsharing signal handlers and the task was created + * using CLONE_THREAD, then must unshare the thread + */ + if ((*flags_ptr & CLONE_SIGHAND) && + (atomic_read(¤t->signal->count) > 1)) + *flags_ptr |= CLONE_THREAD; + + /* + * If unsharing namespace, must also unshare filesystem information. + */ + if (*flags_ptr & CLONE_NEWNS) + *flags_ptr |= CLONE_FS; +} + +/* + * Unsharing of tasks created with CLONE_THREAD is not supported yet + */ +static int unshare_thread(unsigned long unshare_flags) +{ + if (unshare_flags & CLONE_THREAD) + return -EINVAL; + + return 0; +} + +/* + * Unsharing of fs info for tasks created with CLONE_FS is not supported yet + */ +static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) +{ + struct fs_struct *fs = current->fs; + + if ((unshare_flags & CLONE_FS) && + (fs && atomic_read(&fs->count) > 1)) + return -EINVAL; + + return 0; +} + +/* + * Unsharing of namespace for tasks created without CLONE_NEWNS is not + * supported yet + */ +static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp) +{ + struct namespace *ns = current->namespace; + + if ((unshare_flags & CLONE_NEWNS) && + (ns && atomic_read(&ns->count) > 1)) + return -EINVAL; + + return 0; +} + +/* + * Unsharing of sighand for tasks created with CLONE_SIGHAND is not + * supported yet + */ +static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) +{ + struct sighand_struct *sigh = current->sighand; + + if ((unshare_flags & CLONE_SIGHAND) && + (sigh && atomic_read(&sigh->count) > 1)) + return -EINVAL; + else + return 0; +} + +/* + * Unsharing of vm for tasks created with CLONE_VM is not supported yet + */ +static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) +{ + struct mm_struct *mm = current->mm; + + if ((unshare_flags & CLONE_VM) && + (mm && atomic_read(&mm->mm_users) > 1)) + return -EINVAL; + + return 0; + +} + +/* + * Unsharing of files for tasks created with CLONE_FILES is not supported yet + */ +static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) +{ + struct files_struct *fd = current->files; + + if ((unshare_flags & CLONE_FILES) && + (fd && atomic_read(&fd->count) > 1)) + return -EINVAL; + + return 0; +} + +/* + * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not + * supported yet + */ +static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) +{ + if (unshare_flags & CLONE_SYSVSEM) + return -EINVAL; + + return 0; +} + +/* + * unshare allows a process to 'unshare' part of the process + * context which was originally shared using clone. copy_* + * functions used by do_fork() cannot be used here directly + * because they modify an inactive task_struct that is being + * constructed. Here we are modifying the current, active, + * task_struct. + */ +asmlinkage long sys_unshare(unsigned long unshare_flags) +{ + int err = 0; + struct fs_struct *fs, *new_fs = NULL; + struct namespace *ns, *new_ns = NULL; + struct sighand_struct *sigh, *new_sigh = NULL; + struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; + struct files_struct *fd, *new_fd = NULL; + struct sem_undo_list *new_ulist = NULL; + + check_unshare_flags(&unshare_flags); + + if ((err = unshare_thread(unshare_flags))) + goto bad_unshare_out; + if ((err = unshare_fs(unshare_flags, &new_fs))) + goto bad_unshare_cleanup_thread; + if ((err = unshare_namespace(unshare_flags, &new_ns))) + goto bad_unshare_cleanup_fs; + if ((err = unshare_sighand(unshare_flags, &new_sigh))) + goto bad_unshare_cleanup_ns; + if ((err = unshare_vm(unshare_flags, &new_mm))) + goto bad_unshare_cleanup_sigh; + if ((err = unshare_fd(unshare_flags, &new_fd))) + goto bad_unshare_cleanup_vm; + if ((err = unshare_semundo(unshare_flags, &new_ulist))) + goto bad_unshare_cleanup_fd; + + if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) { + + task_lock(current); + + if (new_fs) { + fs = current->fs; + current->fs = new_fs; + new_fs = fs; + } + + if (new_ns) { + ns = current->namespace; + current->namespace = new_ns; + new_ns = ns; + } + + if (new_sigh) { + sigh = current->sighand; + current->sighand = new_sigh; + new_sigh = sigh; + } + + if (new_mm) { + mm = current->mm; + active_mm = current->active_mm; + current->mm = new_mm; + current->active_mm = new_mm; + activate_mm(active_mm, new_mm); + new_mm = mm; + } + + if (new_fd) { + fd = current->files; + current->files = new_fd; + new_fd = fd; + } + + task_unlock(current); + } + +bad_unshare_cleanup_fd: + if (new_fd) + put_files_struct(new_fd); + +bad_unshare_cleanup_vm: + if (new_mm) + mmput(new_mm); + +bad_unshare_cleanup_sigh: + if (new_sigh) + if (atomic_dec_and_test(&new_sigh->count)) + kmem_cache_free(sighand_cachep, new_sigh); + +bad_unshare_cleanup_ns: + if (new_ns) + put_namespace(new_ns); + +bad_unshare_cleanup_fs: + if (new_fs) + put_fs_struct(new_fs); + +bad_unshare_cleanup_thread: +bad_unshare_out: + return err; +} |