From: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> 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@xxxxxxxxxx> Reviewed-by: Jan Kara <jack@xxxxxxx> Link: https://lore.kernel.org/r/cc17199798312406b90834e433d2cefe8266823d.1648306232.git.christophe.jaillet@xxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- block/genhd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- 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; Patches currently in stable-queue which might be from christophe.jaillet@xxxxxxxxxx are queue-5.15/block-fix-the-maximum-minor-value-is-blk_alloc_ext_minor.patch queue-5.15/power-supply-sbs-charger-don-t-cancel-work-that-is-n.patch queue-5.15/firmware-ti_sci-fix-compilation-failure-when-config_.patch queue-5.15/gpu-host1x-fix-a-memory-leak-in-host1x_remove.patch queue-5.15/fsi-aspeed-fix-a-potential-double-free.patch queue-5.15/misc-alcor_pci-fix-an-error-handling-path.patch queue-5.15/i2c-bcm2835-fix-the-error-handling-in-bcm2835_i2c_pr.patch