block: Fix the maximum minor value is blk_alloc_ext_minor()
authorChristophe JAILLET <christophe.jaillet@wanadoo.fr>
Sat, 26 Mar 2022 14:50:46 +0000 (15:50 +0100)
committerJens Axboe <axboe@kernel.dk>
Mon, 28 Mar 2022 12:34:30 +0000 (06:34 -0600)
commitd1868328dec5ae2cf210111025fcbc71f78dd5ca
tree8dbb62158a9b259e4f838401fcffeb08e6c707c9
parent15583a563cd5a7358e975599b7de7caacd9e9ce9
block: Fix the maximum minor value is blk_alloc_ext_minor()

ida_alloc_range(..., min, max, ...) returns values from min to max,
inclusive.

So, NR_EXT_DEVT is a valid idx returned by blk_alloc_ext_minor().

This is an issue because in device_add_disk(), this value is used in:
   ddev->devt = MKDEV(disk->major, disk->first_minor);
and NR_EXT_DEVT is '(1 << MINORBITS)'.

So, should 'disk->first_minor' be NR_EXT_DEVT, it would overflow.

Fixes: 22ae8ce8b892 ("block: simplify bdev/disk lookup in blkdev_get")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/cc17199798312406b90834e433d2cefe8266823d.1648306232.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block/genhd.c