diff options
| author | Pavel Begunkov <asml.silence@gmail.com> | 2025-04-03 12:29:30 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-05-02 08:02:04 +0200 |
| commit | 6d2753b46452a557a12f7ef1ef4ee6641b4e89d8 (patch) | |
| tree | fc0c0ca46f83cfdb734fadcf32ac8f3491743fdf | |
| parent | a9f9f26858c8edc81b46deb8747ba3d6d417d84e (diff) | |
io_uring: always do atomic put from iowq
[ Upstream commit 390513642ee6763c7ada07f0a1470474986e6c1c ]
io_uring always switches requests to atomic refcounting for iowq
execution before there is any parallilism by setting REQ_F_REFCOUNT,
and the flag is not cleared until the request completes. That should be
fine as long as the compiler doesn't make up a non existing value for
the flags, however KCSAN still complains when the request owner changes
oter flag bits:
BUG: KCSAN: data-race in io_req_task_cancel / io_wq_free_work
...
read to 0xffff888117207448 of 8 bytes by task 3871 on cpu 0:
req_ref_put_and_test io_uring/refs.h:22 [inline]
Skip REQ_F_REFCOUNT checks for iowq, we know it's set.
Reported-by: syzbot+903a2ad71fb3f1e47cf5@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d880bc27fb8c3209b54641be4ff6ac02b0e5789a.1743679736.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | io_uring/io_uring.c | 2 | ||||
| -rw-r--r-- | io_uring/refs.h | 7 |
2 files changed, 8 insertions, 1 deletions
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index d9c02e6b7b92..24b9e9a5105d 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1775,7 +1775,7 @@ struct io_wq_work *io_wq_free_work(struct io_wq_work *work) struct io_kiocb *req = container_of(work, struct io_kiocb, work); struct io_kiocb *nxt = NULL; - if (req_ref_put_and_test(req)) { + if (req_ref_put_and_test_atomic(req)) { if (req->flags & IO_REQ_LINK_FLAGS) nxt = io_req_find_next(req); io_free_req(req); diff --git a/io_uring/refs.h b/io_uring/refs.h index 63982ead9f7d..0d928d87c4ed 100644 --- a/io_uring/refs.h +++ b/io_uring/refs.h @@ -17,6 +17,13 @@ static inline bool req_ref_inc_not_zero(struct io_kiocb *req) return atomic_inc_not_zero(&req->refs); } +static inline bool req_ref_put_and_test_atomic(struct io_kiocb *req) +{ + WARN_ON_ONCE(!(data_race(req->flags) & REQ_F_REFCOUNT)); + WARN_ON_ONCE(req_ref_zero_or_close_to_overflow(req)); + return atomic_dec_and_test(&req->refs); +} + static inline bool req_ref_put_and_test(struct io_kiocb *req) { if (likely(!(req->flags & REQ_F_REFCOUNT))) |