From: Christophe JAILLET christophe.jaillet@wanadoo.fr
commit d1868328dec5ae2cf210111025fcbc71f78dd5ca upstream.
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.164830623... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/genhd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/block/genhd.c +++ b/block/genhd.c @@ -328,7 +328,7 @@ int blk_alloc_ext_minor(void) { int idx;
- idx = ida_alloc_range(&ext_devt_ida, 0, NR_EXT_DEVT, GFP_KERNEL); + idx = ida_alloc_range(&ext_devt_ida, 0, NR_EXT_DEVT - 1, GFP_KERNEL); if (idx == -ENOSPC) return -EBUSY; return idx;