diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/seccomp.c | 448 |
1 files changed, 446 insertions, 2 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 393e029f778a..15b6be97fc09 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -33,12 +33,74 @@ #endif #ifdef CONFIG_SECCOMP_FILTER +#include <linux/file.h> #include <linux/filter.h> #include <linux/pid.h> #include <linux/ptrace.h> #include <linux/security.h> #include <linux/tracehook.h> #include <linux/uaccess.h> +#include <linux/anon_inodes.h> + +enum notify_state { + SECCOMP_NOTIFY_INIT, + SECCOMP_NOTIFY_SENT, + SECCOMP_NOTIFY_REPLIED, +}; + +struct seccomp_knotif { + /* The struct pid of the task whose filter triggered the notification */ + struct task_struct *task; + + /* The "cookie" for this request; this is unique for this filter. */ + u64 id; + + /* + * The seccomp data. This pointer is valid the entire time this + * notification is active, since it comes from __seccomp_filter which + * eclipses the entire lifecycle here. + */ + const struct seccomp_data *data; + + /* + * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a + * struct seccomp_knotif is created and starts out in INIT. Once the + * handler reads the notification off of an FD, it transitions to SENT. + * If a signal is received the state transitions back to INIT and + * another message is sent. When the userspace handler replies, state + * transitions to REPLIED. + */ + enum notify_state state; + + /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */ + int error; + long val; + + /* Signals when this has entered SECCOMP_NOTIFY_REPLIED */ + struct completion ready; + + struct list_head list; +}; + +/** + * struct notification - container for seccomp userspace notifications. Since + * most seccomp filters will not have notification listeners attached and this + * structure is fairly large, we store the notification-specific stuff in a + * separate structure. + * + * @request: A semaphore that users of this notification can wait on for + * changes. Actual reads and writes are still controlled with + * filter->notify_lock. + * @next_id: The id of the next request. + * @notifications: A list of struct seccomp_knotif elements. + * @wqh: A wait queue for poll. + */ +struct notification { + struct semaphore request; + u64 next_id; + struct list_head notifications; + wait_queue_head_t wqh; +}; /** * struct seccomp_filter - container for seccomp BPF programs @@ -50,6 +112,8 @@ * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged * @prev: points to a previously installed, or inherited, filter * @prog: the BPF program to evaluate + * @notif: the struct that holds all notification related information + * @notify_lock: A lock for all notification-related accesses. * * seccomp_filter objects are organized in a tree linked via the @prev * pointer. For any task, it appears to be a singly-linked list starting @@ -66,6 +130,8 @@ struct seccomp_filter { bool log; struct seccomp_filter *prev; struct bpf_prog *prog; + struct notification *notif; + struct mutex notify_lock; }; /* Limit any path through the tree to 256KB worth of instructions. */ @@ -386,6 +452,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) if (!sfilter) return ERR_PTR(-ENOMEM); + mutex_init(&sfilter->notify_lock); ret = bpf_prog_create_from_user(&sfilter->prog, fprog, seccomp_check_filter, save_orig); if (ret < 0) { @@ -479,7 +546,6 @@ static long seccomp_attach_filter(unsigned int flags, static void __get_seccomp_filter(struct seccomp_filter *filter) { - /* Reference count is bounded by the number of total processes. */ refcount_inc(&filter->usage); } @@ -550,11 +616,13 @@ static void seccomp_send_sigsys(int syscall, int reason) #define SECCOMP_LOG_TRACE (1 << 4) #define SECCOMP_LOG_LOG (1 << 5) #define SECCOMP_LOG_ALLOW (1 << 6) +#define SECCOMP_LOG_USER_NOTIF (1 << 7) static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | SECCOMP_LOG_KILL_THREAD | SECCOMP_LOG_TRAP | SECCOMP_LOG_ERRNO | + SECCOMP_LOG_USER_NOTIF | SECCOMP_LOG_TRACE | SECCOMP_LOG_LOG; @@ -575,6 +643,9 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action, case SECCOMP_RET_TRACE: log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; break; + case SECCOMP_RET_USER_NOTIF: + log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF; + break; case SECCOMP_RET_LOG: log = seccomp_actions_logged & SECCOMP_LOG_LOG; break; @@ -646,6 +717,68 @@ void secure_computing_strict(int this_syscall) #else #ifdef CONFIG_SECCOMP_FILTER +static u64 seccomp_next_notify_id(struct seccomp_filter *filter) +{ + /* + * Note: overflow is ok here, the id just needs to be unique per + * filter. + */ + lockdep_assert_held(&filter->notify_lock); + return filter->notif->next_id++; +} + +static void seccomp_do_user_notification(int this_syscall, + struct seccomp_filter *match, + const struct seccomp_data *sd) +{ + int err; + long ret = 0; + struct seccomp_knotif n = {}; + + mutex_lock(&match->notify_lock); + err = -ENOSYS; + if (!match->notif) + goto out; + + n.task = current; + n.state = SECCOMP_NOTIFY_INIT; + n.data = sd; + n.id = seccomp_next_notify_id(match); + init_completion(&n.ready); + list_add(&n.list, &match->notif->notifications); + + up(&match->notif->request); + wake_up_poll(&match->notif->wqh, EPOLLIN | EPOLLRDNORM); + mutex_unlock(&match->notify_lock); + + /* + * This is where we wait for a reply from userspace. + */ + err = wait_for_completion_interruptible(&n.ready); + mutex_lock(&match->notify_lock); + if (err == 0) { + ret = n.val; + err = n.error; + } + + /* + * Note that it's possible the listener died in between the time when + * we were notified of a respons (or a signal) and when we were able to + * re-acquire the lock, so only delete from the list if the + * notification actually exists. + * + * Also note that this test is only valid because there's no way to + * *reattach* to a notifier right now. If one is added, we'll need to + * keep track of the notif itself and make sure they match here. + */ + if (match->notif) + list_del(&n.list); +out: + mutex_unlock(&match->notify_lock); + syscall_set_return_value(current, task_pt_regs(current), + err, ret); +} + static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, const bool recheck_after_trace) { @@ -728,6 +861,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, return 0; + case SECCOMP_RET_USER_NOTIF: + seccomp_do_user_notification(this_syscall, match, sd); + goto skip; + case SECCOMP_RET_LOG: seccomp_log(this_syscall, 0, action, true); return 0; @@ -834,6 +971,263 @@ out: } #ifdef CONFIG_SECCOMP_FILTER +static int seccomp_notify_release(struct inode *inode, struct file *file) +{ + struct seccomp_filter *filter = file->private_data; + struct seccomp_knotif *knotif; + + mutex_lock(&filter->notify_lock); + + /* + * If this file is being closed because e.g. the task who owned it + * died, let's wake everyone up who was waiting on us. + */ + list_for_each_entry(knotif, &filter->notif->notifications, list) { + if (knotif->state == SECCOMP_NOTIFY_REPLIED) + continue; + + knotif->state = SECCOMP_NOTIFY_REPLIED; + knotif->error = -ENOSYS; + knotif->val = 0; + + complete(&knotif->ready); + } + + kfree(filter->notif); + filter->notif = NULL; + mutex_unlock(&filter->notify_lock); + __put_seccomp_filter(filter); + return 0; +} + +static long seccomp_notify_recv(struct seccomp_filter *filter, + void __user *buf) +{ + struct seccomp_knotif *knotif = NULL, *cur; + struct seccomp_notif unotif; + ssize_t ret; + + memset(&unotif, 0, sizeof(unotif)); + + ret = down_interruptible(&filter->notif->request); + if (ret < 0) + return ret; + + mutex_lock(&filter->notify_lock); + list_for_each_entry(cur, &filter->notif->notifications, list) { + if (cur->state == SECCOMP_NOTIFY_INIT) { + knotif = cur; + break; + } + } + + /* + * If we didn't find a notification, it could be that the task was + * interrupted by a fatal signal between the time we were woken and + * when we were able to acquire the rw lock. + */ + if (!knotif) { + ret = -ENOENT; + goto out; + } + + unotif.id = knotif->id; + unotif.pid = task_pid_vnr(knotif->task); + unotif.data = *(knotif->data); + + knotif->state = SECCOMP_NOTIFY_SENT; + wake_up_poll(&filter->notif->wqh, EPOLLOUT | EPOLLWRNORM); + ret = 0; +out: + mutex_unlock(&filter->notify_lock); + + if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) { + ret = -EFAULT; + + /* + * Userspace screwed up. To make sure that we keep this + * notification alive, let's reset it back to INIT. It + * may have died when we released the lock, so we need to make + * sure it's still around. + */ + knotif = NULL; + mutex_lock(&filter->notify_lock); + list_for_each_entry(cur, &filter->notif->notifications, list) { + if (cur->id == unotif.id) { + knotif = cur; + break; + } + } + + if (knotif) { + knotif->state = SECCOMP_NOTIFY_INIT; + up(&filter->notif->request); + } + mutex_unlock(&filter->notify_lock); + } + + return ret; +} + +static long seccomp_notify_send(struct seccomp_filter *filter, + void __user *buf) +{ + struct seccomp_notif_resp resp = {}; + struct seccomp_knotif *knotif = NULL, *cur; + long ret; + + if (copy_from_user(&resp, buf, sizeof(resp))) + return -EFAULT; + + if (resp.flags) + return -EINVAL; + + ret = mutex_lock_interruptible(&filter->notify_lock); + if (ret < 0) + return ret; + + list_for_each_entry(cur, &filter->notif->notifications, list) { + if (cur->id == resp.id) { + knotif = cur; + break; + } + } + + if (!knotif) { + ret = -ENOENT; + goto out; + } + + /* Allow exactly one reply. */ + if (knotif->state != SECCOMP_NOTIFY_SENT) { + ret = -EINPROGRESS; + goto out; + } + + ret = 0; + knotif->state = SECCOMP_NOTIFY_REPLIED; + knotif->error = resp.error; + knotif->val = resp.val; + complete(&knotif->ready); +out: + mutex_unlock(&filter->notify_lock); + return ret; +} + +static long seccomp_notify_id_valid(struct seccomp_filter *filter, + void __user *buf) +{ + struct seccomp_knotif *knotif = NULL; + u64 id; + long ret; + + if (copy_from_user(&id, buf, sizeof(id))) + return -EFAULT; + + ret = mutex_lock_interruptible(&filter->notify_lock); + if (ret < 0) + return ret; + + ret = -ENOENT; + list_for_each_entry(knotif, &filter->notif->notifications, list) { + if (knotif->id == id) { + if (knotif->state == SECCOMP_NOTIFY_SENT) + ret = 0; + goto out; + } + } + +out: + mutex_unlock(&filter->notify_lock); + return ret; +} + +static long seccomp_notify_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct seccomp_filter *filter = file->private_data; + void __user *buf = (void __user *)arg; + + switch (cmd) { + case SECCOMP_IOCTL_NOTIF_RECV: + return seccomp_notify_recv(filter, buf); + case SECCOMP_IOCTL_NOTIF_SEND: + return seccomp_notify_send(filter, buf); + case SECCOMP_IOCTL_NOTIF_ID_VALID: + return seccomp_notify_id_valid(filter, buf); + default: + return -EINVAL; + } +} + +static __poll_t seccomp_notify_poll(struct file *file, + struct poll_table_struct *poll_tab) +{ + struct seccomp_filter *filter = file->private_data; + __poll_t ret = 0; + struct seccomp_knotif *cur; + + poll_wait(file, &filter->notif->wqh, poll_tab); + + ret = mutex_lock_interruptible(&filter->notify_lock); + if (ret < 0) + return EPOLLERR; + + list_for_each_entry(cur, &filter->notif->notifications, list) { + if (cur->state == SECCOMP_NOTIFY_INIT) + ret |= EPOLLIN | EPOLLRDNORM; + if (cur->state == SECCOMP_NOTIFY_SENT) + ret |= EPOLLOUT | EPOLLWRNORM; + if ((ret & EPOLLIN) && (ret & EPOLLOUT)) + break; + } + + mutex_unlock(&filter->notify_lock); + + return ret; +} + +static const struct file_operations seccomp_notify_ops = { + .poll = seccomp_notify_poll, + .release = seccomp_notify_release, + .unlocked_ioctl = seccomp_notify_ioctl, +}; + +static struct file *init_listener(struct seccomp_filter *filter) +{ + struct file *ret = ERR_PTR(-EBUSY); + struct seccomp_filter *cur; + + for (cur = current->seccomp.filter; cur; cur = cur->prev) { + if (cur->notif) + goto out; + } + + ret = ERR_PTR(-ENOMEM); + filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL); + if (!filter->notif) + goto out; + + sema_init(&filter->notif->request, 0); + filter->notif->next_id = get_random_u64(); + INIT_LIST_HEAD(&filter->notif->notifications); + init_waitqueue_head(&filter->notif->wqh); + + ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops, + filter, O_RDWR); + if (IS_ERR(ret)) + goto out_notif; + + /* The file has a reference to it now */ + __get_seccomp_filter(filter); + +out_notif: + if (IS_ERR(ret)) + kfree(filter->notif); +out: + return ret; +} + /** * seccomp_set_mode_filter: internal function for setting seccomp filter * @flags: flags to change filter behavior @@ -853,6 +1247,8 @@ static long seccomp_set_mode_filter(unsigned int flags, const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; struct seccomp_filter *prepared = NULL; long ret = -EINVAL; + int listener = -1; + struct file *listener_f = NULL; /* Validate flags. */ if (flags & ~SECCOMP_FILTER_FLAG_MASK) @@ -863,13 +1259,28 @@ static long seccomp_set_mode_filter(unsigned int flags, if (IS_ERR(prepared)) return PTR_ERR(prepared); + if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { + listener = get_unused_fd_flags(O_CLOEXEC); + if (listener < 0) { + ret = listener; + goto out_free; + } + + listener_f = init_listener(prepared); + if (IS_ERR(listener_f)) { + put_unused_fd(listener); + ret = PTR_ERR(listener_f); + goto out_free; + } + } + /* * Make sure we cannot change seccomp or nnp state via TSYNC * while another thread is in the middle of calling exec. */ if (flags & SECCOMP_FILTER_FLAG_TSYNC && mutex_lock_killable(¤t->signal->cred_guard_mutex)) - goto out_free; + goto out_put_fd; spin_lock_irq(¤t->sighand->siglock); @@ -887,6 +1298,16 @@ out: spin_unlock_irq(¤t->sighand->siglock); if (flags & SECCOMP_FILTER_FLAG_TSYNC) mutex_unlock(¤t->signal->cred_guard_mutex); +out_put_fd: + if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { + if (ret < 0) { + fput(listener_f); + put_unused_fd(listener); + } else { + fd_install(listener, listener_f); + ret = listener; + } + } out_free: seccomp_filter_free(prepared); return ret; @@ -911,6 +1332,7 @@ static long seccomp_get_action_avail(const char __user *uaction) case SECCOMP_RET_KILL_THREAD: case SECCOMP_RET_TRAP: case SECCOMP_RET_ERRNO: + case SECCOMP_RET_USER_NOTIF: case SECCOMP_RET_TRACE: case SECCOMP_RET_LOG: case SECCOMP_RET_ALLOW: @@ -922,6 +1344,20 @@ static long seccomp_get_action_avail(const char __user *uaction) return 0; } +static long seccomp_get_notif_sizes(void __user *usizes) +{ + struct seccomp_notif_sizes sizes = { + .seccomp_notif = sizeof(struct seccomp_notif), + .seccomp_notif_resp = sizeof(struct seccomp_notif_resp), + .seccomp_data = sizeof(struct seccomp_data), + }; + + if (copy_to_user(usizes, &sizes, sizeof(sizes))) + return -EFAULT; + + return 0; +} + /* Common entry point for both prctl and syscall. */ static long do_seccomp(unsigned int op, unsigned int flags, void __user *uargs) @@ -938,6 +1374,11 @@ static long do_seccomp(unsigned int op, unsigned int flags, return -EINVAL; return seccomp_get_action_avail(uargs); + case SECCOMP_GET_NOTIF_SIZES: + if (flags != 0) + return -EINVAL; + + return seccomp_get_notif_sizes(uargs); default: return -EINVAL; } @@ -1111,6 +1552,7 @@ long seccomp_get_metadata(struct task_struct *task, #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" #define SECCOMP_RET_TRAP_NAME "trap" #define SECCOMP_RET_ERRNO_NAME "errno" +#define SECCOMP_RET_USER_NOTIF_NAME "user_notif" #define SECCOMP_RET_TRACE_NAME "trace" #define SECCOMP_RET_LOG_NAME "log" #define SECCOMP_RET_ALLOW_NAME "allow" @@ -1120,6 +1562,7 @@ static const char seccomp_actions_avail[] = SECCOMP_RET_KILL_THREAD_NAME " " SECCOMP_RET_TRAP_NAME " " SECCOMP_RET_ERRNO_NAME " " + SECCOMP_RET_USER_NOTIF_NAME " " SECCOMP_RET_TRACE_NAME " " SECCOMP_RET_LOG_NAME " " SECCOMP_RET_ALLOW_NAME; @@ -1134,6 +1577,7 @@ static const struct seccomp_log_name seccomp_log_names[] = { { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, + { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME }, { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, |