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Reimplement RLIMIT_SIGPENDING on top of ucounts
The rlimit counter is tied to uid in the user_namespace. This allows rlimit values to be specified in userns even if they are already globally exceeded by the user. However, the value of the previous user_namespaces cannot be exceeded. Changelog v11: * Revert most of changes to fix performance issues. v10: * Fix memory leak on get_ucounts failure. Signed-off-by: Alexey Gladkov <legion@kernel.org> Link: https://lkml.kernel.org/r/df9d7764dddd50f28616b7840de74ec0f81711a8.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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@ -284,7 +284,7 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p)
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collect_sigign_sigcatch(p, &ignored, &caught);
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num_threads = get_nr_threads(p);
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rcu_read_lock(); /* FIXME: is this correct? */
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qsize = atomic_read(&__task_cred(p)->user->sigpending);
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qsize = get_ucounts_value(task_ucounts(p), UCOUNT_RLIMIT_SIGPENDING);
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rcu_read_unlock();
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qlim = task_rlimit(p, RLIMIT_SIGPENDING);
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unlock_task_sighand(p, &flags);
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@ -12,7 +12,6 @@
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*/
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struct user_struct {
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refcount_t __count; /* reference count */
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atomic_t sigpending; /* How many pending signals does this user have? */
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#ifdef CONFIG_FANOTIFY
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atomic_t fanotify_listeners;
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#endif
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@ -13,6 +13,8 @@ typedef struct kernel_siginfo {
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__SIGINFO;
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} kernel_siginfo_t;
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struct ucounts;
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/*
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* Real Time signals may be queued.
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*/
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@ -21,7 +23,7 @@ struct sigqueue {
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struct list_head list;
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int flags;
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kernel_siginfo_t info;
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struct user_struct *user;
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struct ucounts *ucounts;
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};
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/* flags values. */
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@ -52,6 +52,7 @@ enum ucount_type {
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#endif
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UCOUNT_RLIMIT_NPROC,
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UCOUNT_RLIMIT_MSGQUEUE,
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UCOUNT_RLIMIT_SIGPENDING,
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UCOUNT_COUNTS,
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};
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@ -824,6 +824,7 @@ void __init fork_init(void)
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init_user_ns.ucount_max[UCOUNT_RLIMIT_NPROC] = task_rlimit(&init_task, RLIMIT_NPROC);
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init_user_ns.ucount_max[UCOUNT_RLIMIT_MSGQUEUE] = task_rlimit(&init_task, RLIMIT_MSGQUEUE);
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init_user_ns.ucount_max[UCOUNT_RLIMIT_SIGPENDING] = task_rlimit(&init_task, RLIMIT_SIGPENDING);
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#ifdef CONFIG_VMAP_STACK
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cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
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@ -413,8 +413,8 @@ static struct sigqueue *
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__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
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{
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struct sigqueue *q = NULL;
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struct user_struct *user;
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int sigpending;
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struct ucounts *ucounts = NULL;
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long sigpending;
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/*
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* Protect access to @t credentials. This can go away when all
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@ -425,27 +425,26 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi
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* changes from/to zero.
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*/
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rcu_read_lock();
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user = __task_cred(t)->user;
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sigpending = atomic_inc_return(&user->sigpending);
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ucounts = task_ucounts(t);
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sigpending = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING, 1);
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if (sigpending == 1)
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get_uid(user);
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ucounts = get_ucounts(ucounts);
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rcu_read_unlock();
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if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
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if (override_rlimit || (sigpending < LONG_MAX && sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
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q = kmem_cache_alloc(sigqueue_cachep, flags);
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} else {
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print_dropped_signal(sig);
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}
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if (unlikely(q == NULL)) {
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if (atomic_dec_and_test(&user->sigpending))
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free_uid(user);
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if (ucounts && dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING, 1))
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put_ucounts(ucounts);
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} else {
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INIT_LIST_HEAD(&q->list);
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q->flags = 0;
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q->user = user;
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q->ucounts = ucounts;
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}
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return q;
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}
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@ -453,8 +452,10 @@ static void __sigqueue_free(struct sigqueue *q)
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{
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if (q->flags & SIGQUEUE_PREALLOC)
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return;
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if (atomic_dec_and_test(&q->user->sigpending))
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free_uid(q->user);
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if (q->ucounts && dec_rlimit_ucounts(q->ucounts, UCOUNT_RLIMIT_SIGPENDING, 1)) {
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put_ucounts(q->ucounts);
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q->ucounts = NULL;
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}
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kmem_cache_free(sigqueue_cachep, q);
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}
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@ -80,6 +80,7 @@ static struct ctl_table user_table[] = {
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UCOUNT_ENTRY("max_inotify_instances"),
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UCOUNT_ENTRY("max_inotify_watches"),
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#endif
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{ },
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{ },
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{ },
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{ }
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@ -98,7 +98,6 @@ static DEFINE_SPINLOCK(uidhash_lock);
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/* root_user.__count is 1, for init task cred */
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struct user_struct root_user = {
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.__count = REFCOUNT_INIT(1),
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.sigpending = ATOMIC_INIT(0),
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.locked_shm = 0,
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.uid = GLOBAL_ROOT_UID,
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.ratelimit = RATELIMIT_STATE_INIT(root_user.ratelimit, 0, 0),
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@ -124,6 +124,7 @@ int create_user_ns(struct cred *new)
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}
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ns->ucount_max[UCOUNT_RLIMIT_NPROC] = rlimit(RLIMIT_NPROC);
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ns->ucount_max[UCOUNT_RLIMIT_MSGQUEUE] = rlimit(RLIMIT_MSGQUEUE);
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ns->ucount_max[UCOUNT_RLIMIT_SIGPENDING] = rlimit(RLIMIT_SIGPENDING);
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ns->ucounts = ucounts;
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/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
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