nvme-core: check for too small lba shift

The block layer doesn't support logical block sizes smaller than 512
bytes. The nvme spec doesn't support that small either, but the driver
isn't checking to make sure the device responded with usable data.
Failing to catch this will result in a kernel bug, either from a
division by zero when stacking, or a zero length bio.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: keithbusch

drivers/nvme/host/core.c

@@ -1901,9 +1901,10 @@ static void nvme_update_disk_info(struct gendisk *disk,
 
 	/*
 	 * The block layer can't support LBA sizes larger than the page size
-	 * yet, so catch this early and don't allow block I/O.
+	 * or smaller than a sector size yet, so catch this early and don't
+	 * allow block I/O.
 	 */
-	if (ns->lba_shift > PAGE_SHIFT) {
+	if (ns->lba_shift > PAGE_SHIFT || ns->lba_shift < SECTOR_SHIFT) {
 		capacity = 0;
 		bs = (1 << 9);
 	}