From: Jens Axboe axboe@kernel.dk
[ Upstream commit 5e929367468c8f97cd1ffb0417316cecfebef94b ]
The fix for not advancing the iterator if we're using fixed buffers is broken in that it can hit a condition where we don't terminate the loop. This results in io-wq looping forever, asking to read (or write) 0 bytes for every subsequent loop.
Reported-by: Joel Jaeschke joel.jaeschke@gmail.com Link: https://github.com/axboe/liburing/issues/549 Fixes: 16c8d2df7ec0 ("io_uring: ensure symmetry in handling iter types in loop_rw_iter()") Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/io_uring.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index fd188b972151..82f1311dab8e 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -3220,13 +3220,15 @@ static ssize_t loop_rw_iter(int rw, struct io_kiocb *req, struct iov_iter *iter) ret = nr; break; } + ret += nr; if (!iov_iter_is_bvec(iter)) { iov_iter_advance(iter, nr); } else { - req->rw.len -= nr; req->rw.addr += nr; + req->rw.len -= nr; + if (!req->rw.len) + break; } - ret += nr; if (nr != iovec.iov_len) break; }