io_uring/fdinfo: annotate racy sq/cq head/tail reads

[ Upstream commit f024d3a8 ]

syzbot complains about the cached sq head read, and it's totally right.
But we don't need to care, it's just reading fdinfo, and reading the
CQ or SQ tail/head entries are known racy in that they are just a view
into that very instant and may of course be outdated by the time they
are reported.

Annotate both the SQ head and CQ tail read with data_race() to avoid
this syzbot complaint.

Link: https://lore.kernel.org/io-uring/6811f6dc.050a0220.39e3a1.0d0e.GAE@google.com/


Reported-by:  <syzbot+3e77fd302e99f5af9394@syzkaller.appspotmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>