[PATCH AUTOSEL 5.9 029/147] io_uring: don't set COMP_LOCKED if won't put

Sasha Levin
2020-10-26T23:50:16Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit 368c5481ae7c6a9719c40984faea35480d9f4872 ]

__io_kill_linked_timeout() sets REQ_F_COMP_LOCKED for a linked timeout
even if it can't cancel it, e.g. it's already running. It not only races
with io_link_timeout_fn() for ->flags field, but also leaves the flag
set and so io_link_timeout_fn() may find it and decide that it holds the
lock. Hopefully, the second problem is potential.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index aae0ef2ec34d2..2145cf76a0d6a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1614,6 +1614,7 @@ static bool io_link_cancel_timeout(struct io_kiocb *req)

ret = hrtimer_try_to_cancel(&req->io->timeout.timer);
if (ret != -1) {
+ req->flags |= REQ_F_COMP_LOCKED;
io_cqring_fill_event(req, -ECANCELED);
io_commit_cqring(ctx);
req->flags &= ~REQ_F_LINK_HEAD;
@@ -1636,7 +1637,6 @@ static bool __io_kill_linked_timeout(struct io_kiocb *req)
return false;

list_del_init(&link->link_list);
- link->flags |= REQ_F_COMP_LOCKED;
wake_ev = io_link_cancel_timeout(link);
req->flags &= ~REQ_F_LINK_TIMEOUT;
return wake_ev;
--
2.25.1