From 95036a79e7b56178e2fa9c485114be61d24c1695 Mon Sep 17 00:00:00 2001 From: Andrei Vagin Date: Fri, 28 Jun 2024 02:10:11 +0000 Subject: [PATCH] seccomp: interrupt SECCOMP_IOCTL_NOTIF_RECV when all users have exited SECCOMP_IOCTL_NOTIF_RECV promptly returns when a seccomp filter becomes unused, as a filter without users can't trigger any events. Previously, event listeners had to rely on epoll to detect when all processes had exited. The change is based on the 'commit 99cdb8b9a573 ("seccomp: notify about unused filter")' which implemented (E)POLLHUP notifications. Reviewed-by: Christian Brauner Signed-off-by: Andrei Vagin Reviewed-by: Oleg Nesterov Link: https://lore.kernel.org/r/20240628021014.231976-2-avagin@google.com Reviewed-by: Tycho Andersen Signed-off-by: Kees Cook --- kernel/seccomp.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index e30b60b57614..60990264fef0 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -1466,7 +1466,7 @@ static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int s void *key) { /* Avoid a wakeup if event not interesting for us. */ - if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR))) + if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR | EPOLLHUP))) return 0; return autoremove_wake_function(wait, mode, sync, key); } @@ -1476,6 +1476,9 @@ static int recv_wait_event(struct seccomp_filter *filter) DEFINE_WAIT_FUNC(wait, recv_wake_function); int ret; + if (refcount_read(&filter->users) == 0) + return 0; + if (atomic_dec_if_positive(&filter->notif->requests) >= 0) return 0; @@ -1484,6 +1487,8 @@ static int recv_wait_event(struct seccomp_filter *filter) if (atomic_dec_if_positive(&filter->notif->requests) >= 0) break; + if (refcount_read(&filter->users) == 0) + break; if (ret) return ret;