[PATCH 6.1.y] block: make bio_check_eod work for zero sized devices

["Miguel García" <miguelgarciaroman8@gmail.com>]

From: Christoph Hellwig <hch@lst.de>

commit 3eb96946f0be6bf447cbdf219aba22bc42672f92 upstream.

This patch is a backport.

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+2aca91e1d3ae43aef10c@syzkaller.appspotmail.com
Bug: https://syzkaller.appspot.com/bug?extid=2aca91e1d3ae43aef10c
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>
(cherry picked from commit 3eb96946f0be6bf447cbdf219aba22bc42672f92)
Signed-off-by: Miguel García <miguelgarciaroman8@gmail.com>
---
 block/blk-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 94941e3ce219..6a66f4f6912f 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -515,7 +515,7 @@ 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"
-- 
2.34.1