From: Jens Axboe axboe@kernel.dk
mainline inclusion from mainline-5.9-rc3 commit 9dab14b81807a40dab8e464ec87043935c562c2c category: feature bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27 CVE: NA ---------------------------
There's no point in using the poll handler if we can't do a nonblocking IO attempt of the operation, since we'll need to go async anyway. In fact this is actively harmful, as reading from eg pipes won't return 0 to indicate EOF.
Cc: stable@vger.kernel.org # v5.7+ Reported-by: Benedikt Ames wisp3rwind@posteo.eu Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: yangerkun yangerkun@huawei.com Reviewed-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- fs/io_uring.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index b4d684321724..bf1c73d334c3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4676,12 +4676,20 @@ static bool io_arm_poll_handler(struct io_kiocb *req) struct async_poll *apoll; struct io_poll_table ipt; __poll_t mask, ret; + int rw;
if (!req->file || !file_can_poll(req->file)) return false; if (req->flags & REQ_F_POLLED) return false; - if (!def->pollin && !def->pollout) + if (def->pollin) + rw = READ; + else if (def->pollout) + rw = WRITE; + else + return false; + /* if we can't nonblock try, then no point in arming a poll handler */ + if (!io_file_supports_async(req->file, rw)) return false;
apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);