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

From: Christoph Hellwig <hch@lst.de>
To: axboe@kernel.dk
Cc: minchan@kernel.org, senozhatsky@chromium.org,
	linux-block@vger.kernel.org,
	syzbot+b8d61a58b7c7ebd2c8e0@syzkaller.appspotmail.com
Subject: [PATCH] block: make bio_check_eod work for zero sized devices
Date: Wed, 24 May 2023 08:05:38 +0200	[thread overview]
Message-ID: <20230524060538.1593686-1-hch@lst.de> (raw)

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>
---
 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 00c74330fa92c2..1da77e7d628946 100644
--- 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"
-- 
2.39.2

