block: make bio_check_eod work for zero sized devices

Since the dawn of time bio_check_eod has a check for a non-zero size of
the device.  This doesn't really make any sense as we never want to send
I/O to a device that's been set to zero size, or never moved out of that.

I am a bit surprised we haven't caught this for a long time, but the
removal of the extra validation inside of zram caused syzbot to trip
over this issue recently.  I've added a Fixes tag for that commit, but
the issue really goes back way before git history.

Fixes: 9fe95babc742 ("zram: remove valid_io_request")
Reported-by: syzbot+b8d61a58b7c7ebd2c8e0@syzkaller.appspotmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230524060538.1593686-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 00c74330fa92c221422a629361607068a65eda99..1da77e7d62894651d3e307dbd1be1930983baad8 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -520,7 +520,7 @@ static inline int bio_check_eod(struct bio *bio)
        sector_t maxsector = bdev_nr_sectors(bio->bi_bdev);
        unsigned int nr_sectors = bio_sectors(bio);
 
-       if (nr_sectors && maxsector &&
+       if (nr_sectors &&
            (nr_sectors > maxsector ||
             bio->bi_iter.bi_sector > maxsector - nr_sectors)) {
                pr_info_ratelimited("%s: attempt to access beyond end of device\n"