From: Christophe JAILLET Date: Sat, 26 Mar 2022 14:50:46 +0000 (+0100) Subject: block: Fix the maximum minor value is blk_alloc_ext_minor() X-Git-Tag: v5.16.19~70 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0f8cf8f5ccbad25ed6828875b222dbab29d5c272;p=thirdparty%2Fkernel%2Fstable.git 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 --- diff --git a/block/genhd.c b/block/genhd.c index f6a698f3252b5..2a469f774670f 100644 --- 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;