drivers/block/zram/zram_drv.c: do not keep dangling zcomp pointer after zram reset

We do all reset operations under write lock, so we don't need to save
->disksize and ->comp to stack variables.  Another thing is that ->comp is
freed during zram reset, but comp pointer is not NULL-ed, so zram keeps
the freed pointer value.

Link: https://lkml.kernel.org/r/20220824035100.971816-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 226ea76..add43f6 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1710,9 +1710,6 @@ out:
 
 static void zram_reset_device(struct zram *zram)
 {
-       struct zcomp *comp;
-       u64 disksize;
-
        down_write(&zram->init_lock);
 
        zram->limit_pages = 0;
@@ -1722,17 +1719,15 @@ static void zram_reset_device(struct zram *zram)
                return;
        }
 
-       comp = zram->comp;
-       disksize = zram->disksize;
-       zram->disksize = 0;
-
        set_capacity_and_notify(zram->disk, 0);
        part_stat_set_all(zram->disk->part0, 0);
 
        /* I/O operation under all of CPU are done so let's free */
-       zram_meta_free(zram, disksize);
+       zram_meta_free(zram, zram->disksize);
+       zram->disksize = 0;
        memset(&zram->stats, 0, sizeof(zram->stats));
-       zcomp_destroy(comp);
+       zcomp_destroy(zram->comp);
+       zram->comp = NULL;
        reset_bdev(zram);
 
        up_write(&zram->init_lock);