zram: do not leak page on recompress_store error path

Ensure the page used for local object data is freed on error out path.

Link: https://lkml.kernel.org/r/20250303022425.285971-18-senozhatsky@chromium.org
Fixes: 3f909a60ce ("zram: rework recompress target selection strategy")
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -2013,7 +2013,7 @@ static ssize_t recompress_store(struct device *dev,
 	struct zram_pp_slot *pps;
 	u32 mode = 0, threshold = 0;
 	u32 prio, prio_max;
-	struct page *page;
+	struct page *page = NULL;
 	ssize_t ret;
 
 	prio = ZRAM_SECONDARY_COMP;
@@ -2157,9 +2157,9 @@ next:
 		cond_resched();
 	}
 
-	__free_page(page);
-
 release_init_lock:
+	if (page)
+		__free_page(page);
 	release_pp_ctl(zram, ctl);
 	atomic_set(&zram->pp_in_progress, 0);
 	up_read(&zram->init_lock);