zram: fix potential UAF of zram table

If zram_meta_alloc failed early, it frees allocated zram->table without
setting it NULL. Which will potentially cause zram_meta_free to access
the table if user reset an failed and uninitialized device.

Link: https://lkml.kernel.org/r/[e-mail]
Fixes: 74363ec674cb ("zram: fix uninitialized ZRAM not releasing backing device")
Signed-off-by: Kairui Song <[e-mail]>
Reviewed-by: Sergey Senozhatsky <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

drivers/block/zram/zram_drv.c

···
 	zram->mem_pool = zs_create_pool(zram->disk->disk_name);
 	if (!zram->mem_pool) {
 		vfree(zram->table);
+		zram->table = NULL;
 		return false;
 	}