From 5b9ac3727e4abb11c9cfbe9c0781fc05dfdd7cfb Mon Sep 17 00:00:00 2001 From: Christophe JAILLET Date: Sat, 26 Mar 2022 15:50:46 +0100 Subject: [PATCH] block: Fix the maximum minor value is blk_alloc_ext_minor() 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 Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/cc17199798312406b90834e433d2cefe8266823d.1648306232.git.christophe.jaillet@wanadoo.fr Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/genhd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/genhd.c b/block/genhd.c index 0276a2846adf..74e19d67ceab 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -324,7 +324,7 @@ 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;