Messages in this thread Patch in this message | | | From | Andrei Vagin <> | Subject | [PATCH 1/4] seccomp: don't use semaphore and wait_queue together | Date | Mon, 29 Aug 2022 18:43:53 -0700 |
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Here is no reason to use two different primitives that do similar things.
Signed-off-by: Andrei Vagin <avagin@gmail.com> --- kernel/seccomp.c | 38 ++++++++++++++++++++++++++------------ 1 file changed, 26 insertions(+), 12 deletions(-)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c index e9852d1b4a5e..667fd2d89464 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); /* @@ -1388,8 +1388,10 @@ static long seccomp_set_mode_strict(void) #ifdef CONFIG_SECCOMP_FILTER static void seccomp_notify_free(struct seccomp_filter *filter) { - kfree(filter->notif); - filter->notif = NULL; + struct notification *notif = filter->notif; + + WRITE_ONCE(filter->notif, NULL); + kfree_rcu(notif); } static void seccomp_notify_detach(struct seccomp_filter *filter) @@ -1450,6 +1452,16 @@ find_notification(struct seccomp_filter *filter, u64 id) return NULL; } +static bool notify_wakeup(struct seccomp_filter *filter) +{ + bool ret; + + rcu_read_lock(); + ret = atomic_add_unless(&filter->notif->requests, -1, 0); + rcu_read_unlock(); + + return ret; +} static long seccomp_notify_recv(struct seccomp_filter *filter, void __user *buf) @@ -1467,7 +1479,7 @@ static long seccomp_notify_recv(struct seccomp_filter *filter, memset(&unotif, 0, sizeof(unotif)); - ret = down_interruptible(&filter->notif->request); + ret = wait_event_interruptible(filter->wqh, notify_wakeup(filter)); if (ret < 0) return ret; @@ -1515,7 +1527,8 @@ 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); } @@ -1771,15 +1784,15 @@ static const struct file_operations seccomp_notify_ops = { static struct file *init_listener(struct seccomp_filter *filter) { struct file *ret; + struct notification *notif; ret = ERR_PTR(-ENOMEM); - filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL); - if (!filter->notif) + notif = kzalloc(sizeof(*notif), GFP_KERNEL); + if (!notif) goto out; - sema_init(&filter->notif->request, 0); - filter->notif->next_id = get_random_u64(); - INIT_LIST_HEAD(&filter->notif->notifications); + notif->next_id = get_random_u64(); + INIT_LIST_HEAD(¬if->notifications); ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops, filter, O_RDWR); @@ -1788,10 +1801,11 @@ static struct file *init_listener(struct seccomp_filter *filter) /* The file has a reference to it now */ __get_seccomp_filter(filter); + WRITE_ONCE(filter->notif, notif); out_notif: if (IS_ERR(ret)) - seccomp_notify_free(filter); + kfree(notif); out: return ret; } -- 2.37.2
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