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Biederman) To: Alexey Gladkov Cc: LKML , Kernel Hardening , Linux Containers , linux-mm@kvack.org, Alexey Gladkov , Andrew Morton , Christian Brauner , Jann Horn , Jens Axboe , Kees Cook , Linus Torvalds , Oleg Nesterov References: <9c8b24db40a030347652ee58f44028ca1081acfa.1616533074.git.gladkov.alexey@gmail.com> Date: Mon, 05 Apr 2021 11:58:51 -0500 In-Reply-To: <9c8b24db40a030347652ee58f44028ca1081acfa.1616533074.git.gladkov.alexey@gmail.com> (Alexey Gladkov's message of "Tue, 23 Mar 2021 21:59:15 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1lTSYw-000Z25-OY;;;mid=;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/lRCz+abrVYSdzhXtMBllzyd5yG1jeH8w= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v9 6/8] Reimplement RLIMIT_SIGPENDING on top of ucounts X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 73C78E000110 X-Stat-Signature: xq9sa9mutg5gm37yws8th4shu3po1547 Received-SPF: none (xmission.com>: No applicable sender policy available) receiver=imf13; identity=mailfrom; envelope-from=""; helo=out02.mta.xmission.com; client-ip=166.70.13.232 X-HE-DKIM-Result: none/none X-HE-Tag: 1617641935-830791 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: A small bug below. Eric > diff --git a/kernel/signal.c b/kernel/signal.c > index f2a1b898da29..1b537d9de447 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -413,49 +413,44 @@ void task_join_group_stop(struct task_struct *task) > static struct sigqueue * > __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit) > { > - struct sigqueue *q = NULL; > - struct user_struct *user; > - int sigpending; > + struct sigqueue *q = kmem_cache_alloc(sigqueue_cachep, flags); > > - /* > - * Protect access to @t credentials. This can go away when all > - * callers hold rcu read lock. > - * > - * NOTE! A pending signal will hold on to the user refcount, > - * and we get/put the refcount only when the sigpending count > - * changes from/to zero. > - */ > - rcu_read_lock(); > - user = __task_cred(t)->user; > - sigpending = atomic_inc_return(&user->sigpending); > - if (sigpending == 1) > - get_uid(user); > - rcu_read_unlock(); > + if (likely(q != NULL)) { > + bool overlimit; > > - if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) { > - q = kmem_cache_alloc(sigqueue_cachep, flags); > - } else { > - print_dropped_signal(sig); > - } > - > - if (unlikely(q == NULL)) { > - if (atomic_dec_and_test(&user->sigpending)) > - free_uid(user); > - } else { > INIT_LIST_HEAD(&q->list); > q->flags = 0; > - q->user = user; > + > + /* > + * Protect access to @t credentials. This can go away when all > + * callers hold rcu read lock. > + */ > + rcu_read_lock(); > + q->ucounts = get_ucounts(task_ucounts(t)); > + if (q->ucounts) { > + overlimit = inc_rlimit_ucounts_and_test(q->ucounts, UCOUNT_RLIMIT_SIGPENDING, > + 1, task_rlimit(t, RLIMIT_SIGPENDING)); > + > + if (override_rlimit || likely(!overlimit)) { > + rcu_read_unlock(); > + return q; > + } > + } > + rcu_read_unlock(); I believe you need to call __sigqueue_free here. > } > > - return q; > + print_dropped_signal(sig); > + return NULL; > } > > static void __sigqueue_free(struct sigqueue *q) > { > if (q->flags & SIGQUEUE_PREALLOC) > return; > - if (atomic_dec_and_test(&q->user->sigpending)) > - free_uid(q->user); > + if (q->ucounts) { > + dec_rlimit_ucounts(q->ucounts, UCOUNT_RLIMIT_SIGPENDING, 1); > + put_ucounts(q->ucounts); > + } > kmem_cache_free(sigqueue_cachep, q); > } > Eric