From: Andrei Vagin <avagin@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Christian Brauner <brauner@kernel.org>,
Andrei Vagin <avagin@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
Juri Lelli <juri.lelli@redhat.com>,
Peter Oskolkov <posk@google.com>,
Tycho Andersen <tycho@tycho.pizza>,
Will Drewry <wad@chromium.org>
Subject: [PATCH 1/5] seccomp: don't use semaphore and wait_queue together
Date: Tue, 10 Jan 2023 13:30:06 -0800 [thread overview]
Message-ID: <20230110213010.2683185-2-avagin@google.com> (raw)
In-Reply-To: <20230110213010.2683185-1-avagin@google.com>
From: Andrei Vagin <avagin@gmail.com>
The main reason is to use new wake_up helpers that will be added in the
following patches. But here are a few other reasons:
* if we use two different ways, we always need to call them both. This
patch fixes seccomp_notify_recv where we forgot to call wake_up_poll
in the error path.
* If we use one primitive, we can control how many waiters are woken up
for each request. Our goal is to wake up just one that will handle a
request. Right now, wake_up_poll can wake up one waiter and
up(&match->notif->request) can wake up one more.
Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
kernel/seccomp.c | 41 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 36 insertions(+), 5 deletions(-)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index e9852d1b4a5e..876022e9c88c 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -145,7 +145,7 @@ struct seccomp_kaddfd {
* @notifications: A list of struct seccomp_knotif elements.
*/
struct notification {
- struct semaphore request;
+ atomic_t requests;
u64 next_id;
struct list_head notifications;
};
@@ -1116,7 +1116,7 @@ static int seccomp_do_user_notification(int this_syscall,
list_add_tail(&n.list, &match->notif->notifications);
INIT_LIST_HEAD(&n.addfd);
- up(&match->notif->request);
+ atomic_add(1, &match->notif->requests);
wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM);
/*
@@ -1450,6 +1450,37 @@ find_notification(struct seccomp_filter *filter, u64 id)
return NULL;
}
+static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync,
+ void *key)
+{
+ /* Avoid a wakeup if event not interesting for us. */
+ if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR)))
+ return 0;
+ return autoremove_wake_function(wait, mode, sync, key);
+}
+
+static int recv_wait_event(struct seccomp_filter *filter)
+{
+ DEFINE_WAIT_FUNC(wait, recv_wake_function);
+ int ret;
+
+ if (atomic_add_unless(&filter->notif->requests, -1, 0) != 0)
+ return 0;
+
+ for (;;) {
+ ret = prepare_to_wait_event(&filter->wqh, &wait, TASK_INTERRUPTIBLE);
+
+ if (atomic_add_unless(&filter->notif->requests, -1, 0) != 0)
+ break;
+
+ if (ret)
+ return ret;
+
+ schedule();
+ }
+ finish_wait(&filter->wqh, &wait);
+ return 0;
+}
static long seccomp_notify_recv(struct seccomp_filter *filter,
void __user *buf)
@@ -1467,7 +1498,7 @@ static long seccomp_notify_recv(struct seccomp_filter *filter,
memset(&unotif, 0, sizeof(unotif));
- ret = down_interruptible(&filter->notif->request);
+ ret = recv_wait_event(filter);
if (ret < 0)
return ret;
@@ -1515,7 +1546,8 @@ static long seccomp_notify_recv(struct seccomp_filter *filter,
if (should_sleep_killable(filter, knotif))
complete(&knotif->ready);
knotif->state = SECCOMP_NOTIFY_INIT;
- up(&filter->notif->request);
+ atomic_add(1, &filter->notif->requests);
+ wake_up_poll(&filter->wqh, EPOLLIN | EPOLLRDNORM);
}
mutex_unlock(&filter->notify_lock);
}
@@ -1777,7 +1809,6 @@ static struct file *init_listener(struct seccomp_filter *filter)
if (!filter->notif)
goto out;
- sema_init(&filter->notif->request, 0);
filter->notif->next_id = get_random_u64();
INIT_LIST_HEAD(&filter->notif->notifications);
--
2.39.0.314.g84b9a713c41-goog
next prev parent reply other threads:[~2023-01-10 21:31 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-10 21:30 [PATCH 0/5 v3 RESEND] seccomp: add the synchronous mode for seccomp_unotify Andrei Vagin
2023-01-10 21:30 ` Andrei Vagin [this message]
2023-01-12 14:58 ` [PATCH 1/5] seccomp: don't use semaphore and wait_queue together Tycho Andersen
2023-01-13 21:51 ` Andrei Vagin
2023-01-16 9:48 ` Peter Zijlstra
2023-01-10 21:30 ` [PATCH 2/5] sched: add WF_CURRENT_CPU and externise ttwu Andrei Vagin
2023-01-12 7:35 ` Chen Yu
2023-01-13 21:39 ` Andrei Vagin
2023-01-14 15:59 ` Chen Yu
2023-01-18 6:10 ` Andrei Vagin
2023-01-10 21:30 ` [PATCH 3/5] sched: add a few helpers to wake up tasks on the current cpu Andrei Vagin
2023-01-16 9:59 ` Peter Zijlstra
2023-01-19 6:45 ` Andrei Vagin
2023-01-19 10:09 ` Peter Zijlstra
2023-01-10 21:30 ` [PATCH 4/5] seccomp: add the synchronous mode for seccomp_unotify Andrei Vagin
2023-01-12 15:00 ` Tycho Andersen
2023-01-14 1:16 ` Andrei Vagin
2023-01-10 21:30 ` [PATCH 5/5] selftest/seccomp: add a new test for the sync mode of seccomp_user_notify Andrei Vagin
-- strict thread matches above, loose matches on Subject: below --
2022-11-11 7:31 [PATCH 0/5 v3] seccomp: add the synchronous mode for seccomp_unotify Andrei Vagin
2022-11-11 7:31 ` [PATCH 1/5] seccomp: don't use semaphore and wait_queue together Andrei Vagin
2022-10-20 1:10 [PATCH 0/5 v2] seccomp: add the synchronous mode for seccomp_unotify Andrei Vagin
2022-10-20 1:10 ` [PATCH 1/5] seccomp: don't use semaphore and wait_queue together Andrei Vagin
2022-10-20 5:10 ` Kees Cook
2022-10-21 4:30 ` Andrei Vagin
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