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seccomp: interrupt SECCOMP_IOCTL_NOTIF_RECV when all users have exited

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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 99cdb8b9a5 ("seccomp: notify about
unused filter")' which implemented (E)POLLHUP notifications.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrei Vagin <avagin@google.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240628021014.231976-2-avagin@google.com
Reviewed-by: Tycho Andersen <tandersen@netflix.com>
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Andrei Vagin 2024-06-28 02:10:11 +00:00 committed by Kees Cook
parent c3f38fa61a
commit 95036a79e7
1 changed files with 6 additions and 1 deletions
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7
kernel/seccomp.c
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@ -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;