blkdev_read_iter() has a few odd checks, like gating the position and
count adjustment on whether or not the result is bigger-than-or-equal to
zero (where bigger than makes more sense), and not checking the return
value of blkdev_direct_IO() before doing an iov_iter_revert(). The
latter can lead to attempting to revert with a negative value, which
when passed to iov_iter_revert() as an unsigned value will lead to
throwing a WARN_ON() because unroll is bigger than MAX_RW_COUNT.
Be sane and don't revert for -EIOCBQUEUED, like what is done in other
spots.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
diff --git a/block/fops.c b/block/fops.c
index 6d5c4fc5a216..be9f1dbea9ce 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -783,11 +783,12 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
file_accessed(iocb->ki_filp);
ret = blkdev_direct_IO(iocb, to);
- if (ret >= 0) {
+ if (ret > 0) {
iocb->ki_pos += ret;
count -= ret;
}
- iov_iter_revert(to, count - iov_iter_count(to));
+ if (ret != -EIOCBQUEUED)
+ iov_iter_revert(to, count - iov_iter_count(to));
if (ret < 0 || !count)
goto reexpand;
}
--
Jens Axboe
