From: Eric Biggers <ebiggers@kernel.org>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
Benjamin LaHaise <bcrl@kvack.org>
Cc: linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, Ramji Jiyani <ramjiyani@google.com>,
Christoph Hellwig <hch@lst.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>, Jens Axboe <axboe@kernel.dk>,
Martijn Coenen <maco@android.com>,
stable@vger.kernel.org
Subject: [PATCH v2 2/5] binder: use wake_up_pollfree()
Date: Tue, 7 Dec 2021 01:57:23 -0800 [thread overview]
Message-ID: <20211207095726.169766-3-ebiggers@kernel.org> (raw)
In-Reply-To: <20211207095726.169766-1-ebiggers@kernel.org>
From: Eric Biggers <ebiggers@google.com>
wake_up_poll() uses nr_exclusive=1, so it's not guaranteed to wake up
all non-exclusive waiters. Yet, POLLFREE *must* wake up all waiters.
epoll and aio poll are fortunately not affected by this, but it's very
fragile. Thus, the new function wake_up_pollfree() has been introduced.
Convert binder to use wake_up_pollfree().
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: f5cb779ba163 ("ANDROID: binder: remove waitqueue when thread exits.")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
drivers/android/binder.c | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index cffbe57a8e086..c75fb600740cc 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4422,23 +4422,20 @@ static int binder_thread_release(struct binder_proc *proc,
__release(&t->lock);
/*
- * If this thread used poll, make sure we remove the waitqueue
- * from any epoll data structures holding it with POLLFREE.
- * waitqueue_active() is safe to use here because we're holding
- * the inner lock.
+ * If this thread used poll, make sure we remove the waitqueue from any
+ * poll data structures holding it.
*/
- if ((thread->looper & BINDER_LOOPER_STATE_POLL) &&
- waitqueue_active(&thread->wait)) {
- wake_up_poll(&thread->wait, EPOLLHUP | POLLFREE);
- }
+ if (thread->looper & BINDER_LOOPER_STATE_POLL)
+ wake_up_pollfree(&thread->wait);
binder_inner_proc_unlock(thread->proc);
/*
- * This is needed to avoid races between wake_up_poll() above and
- * and ep_remove_waitqueue() called for other reasons (eg the epoll file
- * descriptor being closed); ep_remove_waitqueue() holds an RCU read
- * lock, so we can be sure it's done after calling synchronize_rcu().
+ * This is needed to avoid races between wake_up_pollfree() above and
+ * someone else removing the last entry from the queue for other reasons
+ * (e.g. ep_remove_wait_queue() being called due to an epoll file
+ * descriptor being closed). Such other users hold an RCU read lock, so
+ * we can be sure they're done after we call synchronize_rcu().
*/
if (thread->looper & BINDER_LOOPER_STATE_POLL)
synchronize_rcu();
--
2.34.1
next prev parent reply other threads:[~2021-12-07 9:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-07 9:57 [PATCH v2 0/5] aio: fix use-after-free and missing wakeups Eric Biggers
2021-12-07 9:57 ` [PATCH v2 1/5] wait: add wake_up_pollfree() Eric Biggers
2021-12-07 9:57 ` Eric Biggers [this message]
2021-12-07 19:11 ` [PATCH v2 2/5] binder: use wake_up_pollfree() Eric Biggers
2021-12-07 9:57 ` [PATCH v2 3/5] signalfd: " Eric Biggers
2021-12-07 9:57 ` [PATCH v2 4/5] aio: keep poll requests on waitqueue until completed Eric Biggers
2021-12-07 9:57 ` [PATCH v2 5/5] aio: fix use-after-free due to missing POLLFREE handling Eric Biggers
2021-12-07 11:17 ` [PATCH v2 0/5] aio: fix use-after-free and missing wakeups Christoph Hellwig
2021-12-07 19:10 ` Eric Biggers
2021-12-07 23:24 ` Linus Torvalds
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